As you learn to use your EOS R5 or R6 creatively, you’re going to find that the right settings—as determined by the camera’s exposure meter and intelligence—need to be adjusted to account for your creative decisions or to fine-tune the image for special situations.

For example, when you shoot with the main light source behind the subject, you end up with backlighting, which results in an overexposed background and/or an underexposed subject. The camera recognizes backlit situations nicely, and can properly base exposure on the main subject, producing a decent photo. Features like Highlight Tone Priority and the Auto Lighting Optimizer can fine-tune exposure to preserve detail in the highlights and shadows.

But what if you want to underexpose the subject, to produce a silhouette effect? Or, perhaps, you might want to use an external electronic flash to fill in the shadows on your subject. The more you know about how to use your camera, the more you’ll run into situations where you want to creatively tweak the exposure to provide a different look than you’d get with a straight shot.

This chapter shows you the fundamentals of exposure, so you’ll be better equipped to override the default settings when you want to or need to. After all, correct exposure is one of the foundations of good photography, along with accurate focus and sharpness, appropriate color balance, freedom from unwanted noise and excessive contrast, as well as pleasing composition.

You have a great deal of control over all of these, although composition is entirely up to you. You must still frame the photograph to create an interesting arrangement of subject matter, but all the other parameters are basic functions of the camera. You can let your camera set them for you automatically, you can fine-tune how it applies its automatic settings, or you can make them yourself, manually. The amount of control you have over exposure, sensitivity (ISO settings), color balance, focus, and image parameters like sharpness and contrast make the camera a versatile tool for creating images.

In the next few pages, I’m going to give you a grounding in one of those foundations, and explain the basics of exposure, either as an introduction or as a refresher course, depending on your current level of expertise. When you finish this chapter, you’ll understand most of what you need to know to take well-exposed photographs creatively in a broad range of situations with the camera.

Getting a Handle on Exposure

In the most basic sense, exposure is all about light. Exposure can make or break your photo. Correct exposure brings out the detail in the areas you want to picture, providing the range of tones and colors you need to create the desired image. Poor exposure can cloak important details in shadow or wash them out in glare-filled featureless expanses of white. However, getting the perfect exposure requires some intelligence—either that built into the camera or the smarts in your head—because digital sensors can’t capture all the tones we can see. If the range of tones in an image is extensive, embracing both inky black shadows and bright highlights, we often must settle for an exposure that renders most of those tones—but not all—in a way that best suits the photo we want to produce.

You’re probably aware of the traditional “exposure triangle” of aperture (quantity of light and light passed by the lens), shutter speed (the amount of time the shutter is open), and the ISO sensitivity of the sensor—all working proportionately and reciprocally to produce an exposure. The trio is itself affected by the amount of illumination that is available. So, if you double the amount of light, increase the aperture by one stop, make the shutter speed twice as long, or boost the ISO setting 2X, you’ll get twice as much exposure. Similarly, you can increase any of these factors while decreasing one of the others by a similar amount to keep the same exposure.

Working with any of the three controls involves trade-offs. Larger f/stops provide less depth-of-field, while smaller f/stops increase depth-of-field (and potentially at the same time can decrease sharpness through a phenomenon called diffraction). Shorter shutter speeds do a better job of reducing the effects of camera/subject motion, while longer shutter speeds make that motion blur more likely. Higher ISO settings increase the amount of visual noise and artifacts in your image, while lower ISO settings reduce the effects of noise. (See Figure 4.1.)

Exposure determines the look, feel, and tone of an image, in more ways than one. Incorrect exposure can impair even the best-composed image by cloaking important tones in darkness, or by washing them out so they become featureless to the eye. On the other hand, correct exposure brings out the detail in the areas you want to picture and provides the range of tones and colors you need to create the desired image. However, getting the perfect exposure can be tricky because digital sensors can’t capture all the tones we can see. If the range of tones in an image is extensive, embracing both inky black shadows and bright highlights, the sensor may not be able to capture them all. Sometimes, we must settle for an exposure that renders most of those tones—but not all—in a way that best suits the photo we want to produce. You’ll often need to make choices about which details are important, and which are not, so that you can grab the tones that truly matter in your image. That’s part of the creativity you bring to bear in realizing your photographic vision.

Figure 4.1 The traditional exposure triangle includes aperture, shutter speed, and ISO sensitivity.

For example, look at two bracketed exposures presented at top in Figure 4.2. For the image at upper left, the darker areas and shadows are well exposed, but the brightest highlights—the ceiling fixtures and the scene outside the windows—are seriously overexposed. The version on the upper right, taken an instant later with the tripod-mounted camera, shows detail in the highlights, but most of the country store’s interior is cloaked in darkness. The camera’s sensor simply can’t capture detail in both dark areas and bright areas in a single shot.

With digital camera sensors, it’s tricky to capture detail in both highlights and shadows in a single image, because the number of tones, the dynamic range of the sensor, is limited. The solution, in this case, was to resort to a technique called High Dynamic Range (HDR) photography, in which the two exposures from Figure 4.2 were combined in an image editor such as Photoshop, or a specialized HDR tool like Photomatix and Aurora HDR (both about $100 from www.hdrsoft.com and www.skylum.com, respectively). The resulting shot is shown at bottom in Figure 4.2. I’ll explain more about HDR photography later in this chapter. For now, though, I’m going to concentrate on showing you how to get the best exposures possible without resorting to such tools, using only the features of your camera.

Figure 4.2 The image is exposed for the interior, losing highlight (upper left). At upper right, the exposure captures detail in the brightest areas of the image, but the interior is seriously underexposed. Combining the two exposures produces the best compromise image (bottom).

To understand exposure, you need to understand the six aspects of light that combine to produce an image. Start with a light source—the sun, an interior lamp, or the glow from a campfire—and trace its path to your camera, through the lens, and finally to the sensor that captures the illumination. Here’s a brief review of the things within our control that affect exposure.

• Light at its source. Our eyes and our cameras—film or digital—are most sensitive to that portion of the electromagnetic spectrum we call visible light. That light has several important aspects that are relevant to photography, such as color and harshness (which is determined primarily by the apparent size of the light source as it illuminates a subject). But, in terms of exposure, the important attribute of a light source is its intensity. We may have direct control over intensity, which might be the case with an interior light that can be brightened or dimmed. Or, we might have only indirect control over intensity, as with sunlight, which can be made to appear dimmer by introducing translucent light-absorbing or reflective materials in its path.
• Light’s duration. We tend to think of most light sources as continuous. But, as you’ll learn in Chapter 9, the duration of light can change quickly enough to modify the exposure, as when the main illumination in a photograph comes from an intermittent source, such as an electronic flash.
• Light reflected, transmitted, or emitted. Once light is produced by its source, either continuously or in a brief burst, we can see and photograph objects by the light that is reflected from our subjects toward the camera lens; transmitted (say, from translucent objects that are lit from behind); or emitted (by a candle or television screen). When more or less light reaches the lens from the subject, we need to adjust the exposure. This part of the equation is under our control to the extent we can increase the amount of light falling on or passing through the subject (by adding extra light sources or using reflectors), or by pumping up the light that’s emitted (by increasing the brightness of the glowing object).
• Light passed by the lens. Not all the illumination that reaches the front of the lens makes it all the way through. Filters can remove some of the light before it enters the lens. Inside the lens barrel is a variable-sized diaphragm that dilates and contracts to vary the size of the aperture and control the amount of light that enters the lens. You, or the camera’s autoexposure system, can control exposure by varying the size of the aperture. The relative size of the aperture is called the f/stop.
• Light passing through the shutter. Once light passes through the lens, the amount of time the sensor receives it is determined by the camera’s shutter, which can remain open for as long as 30 seconds (or even longer if you use the Bulb setting) or as briefly as 1/8000th second.
• Light captured by the sensor. Not all the light falling onto the sensor is captured. If the number of photons reaching a particular photosite doesn’t pass a set threshold, no information is recorded. Similarly, if too much light illuminates a pixel in the sensor, then the excess isn’t recorded or, worse, spills over to contaminate adjacent pixels. We can modify the minimum and maximum number of pixels that contribute to image detail by adjusting the ISO setting. At higher ISOs, the incoming light is amplified to boost the effective sensitivity of the sensor.

These factors—the quantity of light produced by the light source, the amount reflected or transmitted toward the camera, the light passed by the lens, the amount of time the shutter is open, and the sensitivity of the sensor—all work proportionately and reciprocally to produce an exposure. That is, if you double the amount of light that’s available, increase the aperture by one stop, make the shutter speed twice as long, or boost the ISO setting 2X, you’ll get twice as much exposure. Similarly, you can increase any of these factors while decreasing one of the others by a similar amount to keep the same exposure.

Most commonly, exposure settings are made using the aperture and shutter speed, followed by adjusting the ISO sensitivity if it’s not possible to get the preferred exposure; that is, the one that uses the “best” f/stop or shutter speed for the depth-of-field (range of sharp focus) or action stopping we want (produced by short shutter speeds, as I’ll explain later). Table 4.1 shows equivalent exposure settings using various shutter speeds and f/stops.

TABLE 4.1 Equivalent Exposures

When the camera is set for P (Program) mode, the metering system selects the correct exposure for you automatically, but you can change quickly to an equivalent exposure by locking the current exposure (hold the shutter release down halfway, or press the * button), and then spinning the Main Dial until the desired equivalent exposure combination is displayed. You can use this standard Program Shift feature more easily if you remember that you need to rotate the dial toward the left when you want to increase the amount of depth-of-field or use a slower shutter speed; rotate to the right when you want to reduce the depth-of-field or use a faster shutter speed. The need for more/less DOF and slower/faster shutter speed are the primary reasons you’d want to use Program Shift. I’ll explain Program mode exposure shifting options in more detail later in this chapter.

In Aperture-priority (Av) and Shutter-priority (Tv) modes (or Fv mode when you opt to choose either aperture or shutter speed manually), you can change to an equivalent exposure using a different combination of shutter speed and aperture, but only by either adjusting the aperture in Aperture-priority mode (the camera then chooses the shutter speed) or shutter speed in Shutter-priority mode (the camera then selects the aperture). I’ll cover all these exposure modes and their differences later in the chapter.

Correctly Exposed

The image shown in Figure 4.3, left, represents how a photograph might appear if you inserted the patches shown at bottom left into the scene, and then calculated exposure by measuring the light reflecting from the middle gray patch, which, for the sake of illustration, we’ll assume reflects approximately 12 to 18 percent of the light that strikes it. The gray patch also happens to be similar in reflectance to the background behind the subject. The exposure meter in the camera sees an object that it thinks is a middle gray, calculates an exposure based on that, and the patch in the center of the strip is rendered at its proper tonal value. Best of all, because the resulting exposure is correct, the black patch at left and white patch at right are rendered properly as well.

Figure 4.3 Left: When exposure is calculated based on the middle-gray tone in the center of the card, the black and white patches are rendered accurately, too. Center: When exposure is calculated based on the black square, the black patch looks gray, the gray patch appears to be a light gray, and the white square is seriously overexposed. Right: When exposure is calculated based on the white patch on the right, the photo is underexposed.

When you’re shooting pictures with your camera, and the meter happens to base its exposure on a subject that averages that “ideal” middle gray, you’ll end up with similar (accurate) results. The camera’s exposure algorithms are concocted to ensure this kind of result as often as possible, barring any unusual subjects (that is, those that are backlit, or have uneven illumination). The camera has four different metering modes, each of which is equipped to handle certain types of unusual subjects, as I’ll outline.

Overexposed

Figure 4.3, center, shows what would happen if the exposure were calculated based on metering the leftmost, black patch, which is roughly the same tonal value of the darkest areas of the subject’s hair. The light meter sees less light reflecting from the black square than it would see from a gray middle-tone subject, and so figures, “Aha! I need to add exposure to brighten this subject up to a middle gray!” That lightens the “black” patch, so it now appears to be gray.

But now the patch in the middle that was originally middle gray is overexposed and becomes light gray. And the white square at right is now seriously overexposed and loses detail in the highlights, which have become a featureless white. Our human subject is similarly overexposed.

Underexposed

The third possibility in this simplified scenario is that the light meter might measure the illumination bouncing off the white patch, which roughly corresponds to the subject’s blouse, and try to render that tone as a middle gray. A lot of light is reflected by the white square, so the exposure is reduced, bringing that patch closer to a middle-gray tone. The patches that were originally gray and black are now rendered too dark. Clearly, measuring the gray patch—or a substitute that reflects about the same amount of light, such as the standard Kodak gray card sold in many photo stores—is the only way to ensure that the exposure is precisely correct. (See Figure 4.3, right.)

As you can see, the ideal way to measure exposure is to meter from a subject that reflects 12 to 18 percent of the light that reaches it. If you want the most precise exposure calculations, the solution is to use a stand-in, such as the evenly illuminated gray card I just mentioned. But, because the standard Kodak gray card reflects 18 percent of the light that reaches it and your camera is calibrated for a somewhat darker 12 percent tone, you would need to add about one-half stop more exposure than the value metered from the card.

In some very bright scenes (like a snowy landscape or a lava field), you won’t have a mid-tone to meter. Another substitute for a gray card is the palm of a human hand (the backside of the hand is too variable). But a human palm, regardless of ethnic group, is even brighter than a standard gray card, so instead of one-half stop more exposure, you need to add one additional stop. That is, if your meter reading is 1/500th of a second at f/11, use 1/500th second at f/8 or 1/250th second at f/11 instead. (Both exposures are equivalent.)

Choosing a Metering Mode

To calculate exposure automatically, you need to tell the camera where in the frame to measure the light (this is called the metering mode) and what controls should be used (aperture, shutter speed, or both) to set the exposure. That’s called exposure mode, and includes Program (P), Shutter-priority (Tv), Aperture-priority (Av), Flexible-priority (Fv), or Manual (M) options, plus Scene Intelligent Auto. I’ll explain all these next.

But first, I’m going to introduce you to the four metering modes. You can select any of the four if you’re working with P, Tv, Av, or M exposure modes; if you’re using Scene Intelligent Auto, Evaluative metering is selected automatically and cannot be changed. In Live View mode, only Evaluative and Center-weighted averaging modes can be selected.

Choose a metering mode by pressing the Q button and navigating to the Metering Mode icon, which is fifth from the top in the left column. (See Figure 4.4.) Then use either dial to select the mode you want, and press SET to confirm.

Figure 4.4 Use the Quick Control menu to choose a metering mode.

Available modes include:

• Evaluative. The camera slices up the frame into 384 different zones (a 24 × 16 matrix), shown as yellow rectangles in Figure 4.5. (Don’t confuse these zones with the autofocus points or zones; they are different.)

  The exposure zones used are linked to the autofocus system such that as the camera evaluates the measurements, it gives extra emphasis to the metering zones that indicate sharp focus. From this data, it makes an educated guess about what kind of picture you’re taking, based on examination of thousands of different real-world photos in the camera’s database. For example, if the top sections of a picture are much lighter than the bottom portions, the algorithm can assume that the scene is a landscape photo with lots of sky. This mode is the best all-purpose metering method for most pictures. I’ll explain how to choose an autofocus/exposure zone in the section on autofocus operation later in this chapter.

  Note: Evaluative metering is sometimes described as a type of full-frame averaging. That’s absolutely incorrect. The camera intelligently considers the differences between the measured zones and then classifies what type of scene is being evaluated before calculating an exposure. Two subjects could have exactly the same average illumination but require quite different exposures, depending on the location of the bright, dark, and midtone areas of the scene.

• Partial. This is a faux spot mode, using roughly 6.1 (R5) or 5.8 (R6) percent of the image area to calculate exposure, which, as you can see in Figure 4.6, is a rather large spot, represented by the larger yellow circle. Use this mode if the background is much brighter or darker than the subject, as in the figure.
• Spot. This mode confines the reading to a limited area in the center of the viewfinder, as shown in Figure 4.7, making up only 3.1 (R5) or 2.9 (R6) percent of the image. This mode is useful when you want to base exposure on a small area in the frame, such as the gray portions of the structure in the figure. If that area is in the center of the frame, so much the better. If not, you’ll have to make your meter reading and then lock exposure by pressing the shutter release halfway, or by pressing the AE lock (*) button. Note that spot metering is not linked to the focus point.

Figure 4.5 Evaluative metering uses 384 zones and is effective for interpreting evenly lit scenes.

Figure 4.6 Partial metering uses a center spot that’s roughly 6.1 percent (R5) [5.8 percent (R6)] of the frame area and is excellent for images with the most important areas in the center.

Figure 4.7 Spot metering calculates exposure based on a center spot that’s only 3.1 percent (R5) [2.9 percent (R6)] of the image area and allows measuring specific areas, such as the gray portions of this structure.

Figure 4.8 Center-weighted metering calculates exposure based on the full frame but emphasizes the center area. Exposure for the example image was calculated from the large area in the center of the frame, with less emphasis on the darker surroundings.

• Center-weighted averaging. In this mode, the exposure meter emphasizes a zone in the center of the frame to calculate exposure, as shown in Figure 4.8, on the theory that, for most pictures, the main subject will be located in the center. Center-weighting works best for portraits, architectural photos, and other pictures in which the most important subject is located in the middle of the frame, as in the figure. As the name suggests, the light reading is weighted toward the central portion, but information is also used from the rest of the frame. If your main subject is surrounded by very bright or very dark areas, the exposure might not be exactly right. However, this scheme works well in many situations if you don’t want to use one of the other modes.

Choosing a Shooting Mode

You’ll find five semi-automatic and manual methods for choosing the appropriate shutter speed and aperture, including: Program (P), Shutter-priority (Tv), Aperture-priority (Av), and Manual (M). The fifth method, Flexible-Priority (Fv) can mimic any of the previous four. A sixth, Scene Intelligent Auto (A+), makes all the exposure calculations for you. To select one of these modes, just rotate the Mode Dial located at the top-right side of the R6 (see Figure 4.9, left), or press the MODE button on top of the R5 (see Figure 4.9, right) and use the QCD-1 or QCD-2 dial or the directional controls to cycle among the available exposure modes. Press the INFO button to toggle between still photography and movie modes.

Your choice of which exposure/shooting mode is best for a given shooting situation will depend on things like your need for more/less depth-of-field, a desire to freeze action or allow motion blur, or how much noise you find acceptable in an image. (Remember that exposure triangle at the beginning of the chapter?) Each of the camera’s exposure methods emphasizes one of those aspects of image capture or another. This section introduces you to all of them.

Figure 4.9 Select a Shooting mode.

Scene Intelligent Auto Mode

On first consideration, including an exposure mode with almost no user options might seem counterintuitive on your advanced camera, because it essentially transforms a sophisticated pro/enthusiast camera into a point-and-click snapshooter. Delve deeper, and you’ll discover that there is method in Canon’s madness, and that Scene Intelligent Auto is a lot more than a less versatile version of Program mode. The key is the Intelligent part of the mode’s nomenclature.

With P mode (discussed shortly), only the shutter speed and aperture are determined by the camera. You can change the metering mode, autofocus mode, white balance, and virtually all other settings. In Scene Intelligent Auto mode, the camera will analyze your scene, even to the extent of evaluating whether or not your subject is static or moving, and then intelligently choose optimum settings without any input from you. The settings the camera has to work with include:

• ISO speed. The camera will choose an ISO sensitivity automatically.
• Picture Style. The A (automatic) Picture Style is active, and the camera will choose appropriate settings. Note that if you have made changes to the Auto Picture Style (I’ll show you how to do that in Chapter 11), they will be ignored in Scene Intelligent Auto.
• White balance. White balance is set automatically and cannot be changed.
• Auto Lighting Optimizer. Always active in Scene Intelligent Auto mode.
• Color space. Forced to sRGB.
• Autofocus. The camera selects either One-Shot AF or Servo AF when you press the shutter release halfway. You cannot switch from one to the other manually. AF point selection is always automatic, and the AF-assist beam is activated if needed. You can turn Eye Detection on or off by pressing the Q button, highlighting the AF Method icon, and pressing the INFO button.
• Metering mode. Evaluative metering is always used.

Things that you can choose in Scene Intelligent Auto mode include:

• Manual focus. Manual focus can be chosen by toggling the AF/MF switch on the lens to Manual.
• Touch focus. You can tap on a person’s face or some other subject within the frame using the touch screen when Continuous AF is set to Disable in the AF 2 menu (as described in Chapter 12).
• Drive mode. You use the Quick Control screen to choose from single shooting, high-/low-speed continuous shooting, silent single shooting, silent continuous shooting, and 10 sec./2 sec. self-timer modes.
• Image quality/size. Press the Q button to select among your RAW, JPEG, and other image size options, including Movie Recording Size.

Some specific Shooting menu options are available from the truncated four-tab menu system offered in Scene Intelligent Auto mode; there are also two Autofocus menu tabs. The available choices are described in more detail in Chapters 11 and 12.

Aperture-Priority Mode

In Av mode, you specify the lens opening used, and the camera selects the shutter speed. Aperture-priority is especially good when you want to use a particular lens opening to achieve a desired effect. Perhaps you’d like to use the smallest f/stop possible to maximize depth-of-field in a close-up picture. Or, you might want to use a large f/stop to throw everything except your main subject out of focus, as in Figure 4.10. Maybe you’d just like to “lock in” a particular f/stop smaller than the maximum aperture because it’s the sharpest available aperture with that lens. Or, you might prefer to use, say, f/2.8 on a lens with a maximum aperture of f/1.4, because you want the best compromise between speed and sharpness.

Aperture-priority can even be used to specify a range of shutter speeds you want to use under varying lighting conditions, which seems almost contradictory. But think about it. You’re shooting a soccer game outdoors with a telephoto lens and want a relatively high shutter speed, but you don’t care if the speed changes a little should the sun duck behind a cloud. Set your camera to Av, and adjust the aperture until a shutter speed of, say, 1/1000th second is selected at your current ISO setting. (In bright sunlight at ISO 400, that aperture is likely to be around f/11.) Then, go ahead and shoot, knowing that your camera will maintain that f/11 aperture (for sufficient DOF as the soccer players move about the field), but will drop down to 1/750th or 1/500th second if necessary, should the lighting change a little.

Figure 4.10 Use Aperture-priority to “lock in” a large f/stop when you want to blur the background.

If the shutter speed in the viewfinder or on the Shooting Settings screen is blinking, that indicates that the camera is unable to select an appropriate shutter speed at the selected aperture and that overexposure (the 8000 is blinking) or underexposure (the 30 shutter speed is blinking) will occur at the current ISO setting. To correct overexposure, select a smaller aperture (if available) or choose a lower ISO sensitivity. Fix underexposure conditions by choosing a larger aperture (if possible) or a higher ISO setting.

That’s the major pitfall of using Av: you might select an f/stop that is too small or too large to allow an optimal exposure with the available shutter speeds. For example, if you choose f/2.8 as your aperture and the illumination is quite bright (say, at the beach or in snow), even your camera’s fastest shutter speed might not be able to cut down the amount of light reaching the sensor to provide the right exposure. Or, if you select f/8 in a dimly lit room, you might find yourself shooting with a very slow shutter speed that can cause blurring from subject movement or camera shake. Aperture-priority is best used by those with a bit of experience in choosing settings. Many seasoned photographers leave their camera set on Av all the time. The Safety Shift feature can be used to automatically override your selected aperture if the camera is unable to obtain a correct exposure. Safety Shift operates even when you’re using flash. I’ll show you how to configure that setting, which can also be used with P, Tv, and Fv modes, in Chapter 15.

When to use Aperture-priority:

• General landscape photography. Your camera has enough resolution to allow making huge, gorgeous prints, as well as smaller prints that are filled with eye-popping detail. Aperture-priority is a good tool for ensuring that your landscape is sharp from foreground to infinity, if you select an f/stop that provides maximum depth-of-field.

  If you use Av mode and select an aperture like f/11 or f/16, it’s your responsibility to make sure the shutter speed selected is fast enough to avoid losing detail to camera shake, or that the camera is mounted on a tripod. One thing that new landscape photographers fail to account for is the movement of distant leaves and tree branches. When seeking the ultimate in sharpness, go ahead and use Aperture-priority, but boost ISO sensitivity a bit, if necessary, to provide a sufficiently fast shutter speed, whether shooting hand-held or with a tripod.

• Specific landscape situations. Aperture-priority is also useful when you have no objection to using a long shutter speed, or, particularly, want the camera to select one. Waterfalls are a perfect example. You can use Av mode, set your camera to ISO 100, use a small f/stop, and let the camera select a longer shutter speed that will allow the water to blur as it flows. Indeed, you might need to use a neutral-density filter to get a sufficiently long shutter speed. But Aperture-priority mode is a good start.
• Portrait photography. Portraits are the most common applications of selective focus. A medium-large aperture (say, f/5.6 or f/8) with a longer lens/zoom setting (in the 85mm–135mm range) will allow the background behind your portrait subject to blur. A very large aperture (I frequently shoot wide open with my 85mm f/1.2 lens) lets you apply selective focus to your subject’s face. With a three-quarters view of your subject, as long as their eyes are sharp, it’s okay if the far ear or their hair is out of focus.
• When you want to ensure optimal sharpness. All lenses have an aperture or two at which they perform best, providing the level of sharpness you expect from a camera with the resolution of the R5/R6. That’s usually about two stops down from wide open, and thus will vary depending on the maximum aperture of the lens. My 85mm f/1.2 is good wide open, but it’s even sharper at f/2.8 or f/4; I shoot my 70-200mm f/2.8 wide open at concerts, but, if I can use f/4 instead, I’ll get better results. Aperture-priority allows me to use each lens at its very best f/stop.
• Close-up/Macro photography. Depth-of-field is typically very shallow when shooting macro photos, and you’ll want to choose your f/stop carefully. Perhaps you need the smallest aperture you can get away with to maximize DOF. Or, you might want to use a wider stop to emphasize your subject, as I did with the photo of the bird in Figure 4.10. Aperture-priority mode comes in very useful when shooting close-up pictures. Because macro work is frequently done with the camera mounted on a tripod, and your close-up subjects, if not living creatures, may not be moving much, a longer shutter speed isn’t a problem. Aperture-priority (Av mode) can be your preferred choice.

Shutter-Priority Mode

Shutter-priority (Tv) is the inverse of Aperture-priority: you choose the shutter speed you’d like to use, and the camera’s metering system selects the appropriate f/stop. Perhaps you’re shooting action photos and you want to use the absolute fastest shutter speed available with your camera; in other cases, you might want to use a slow shutter speed to add some blur to a sports image that would be mundane if the action were completely frozen. Motor sports and track-and-field events particularly lend themselves to creative use of slower speeds, as you can see in Figure 4.11. Shutter-priority mode gives you some control over how much action-freezing capability your digital camera brings to bear in a particular situation.

You’ll also encounter the same problem as with Aperture-priority when you select a shutter speed that’s too long or too short for correct exposure under some conditions. I’ve shot outdoor soccer games on sunny fall evenings and used Shutter-priority mode to lock in a 1/1000th-second shutter speed, which triggered the blinking warning, even with the lens wide open.

Like Av mode, it’s possible to choose an inappropriate shutter speed. If that’s the case, the maximum aperture of your lens (to indicate underexposure) or the minimum aperture (to indicate overexposure) will blink. To fix, select a longer shutter speed or higher ISO setting (for underexposure), or a faster shutter speed/lower ISO setting (for overexposure), or use Safety Shift, mentioned previously.

Figure 4.11 Lock the shutter at a slow speed to introduce a little blur into an action shot, seen here in this panned image of a relay runner.

When to use Shutter-priority:

• To reduce blur from subject motion. Set the shutter speed of the camera to a higher value to reduce the amount of blur from subjects that are moving. The exact speed will vary depending on how fast your subject is moving and how much blur is acceptable. You might want to freeze a basketball player in mid-dunk with a 1/1000th-second shutter speed or use 1/250th second to allow the spinning wheels of a motocross racer to blur a tiny bit to add the feeling of motion.
• To add blur from subject motion. There are times when you want a subject to blur, say, when shooting waterfalls with the camera set for a one- or two-second exposure in Shutter-priority mode.
• To add blur from camera motion when you are moving. Say you’re panning to follow a pair of relay runners. You might want to use Shutter-priority mode and set the camera for 1/60th second, so that the background will blur as you pan with the runners. The shutter speed will be fast enough to provide a sharp image of the athletes.
• To reduce blur from camera motion when you are moving. In other situations, the camera may be in motion, say, because you’re shooting from a moving train or auto, and you want to minimize the amount of blur caused by the motion of the camera. Shutter-priority is a good choice here, too.
• Landscape photography hand-held. If you can’t use a tripod for your landscape shots, you’ll still probably want the sharpest image possible. Shutter-priority can allow you to specify a shutter speed that’s fast enough to reduce or eliminate the effects of camera shake. Just make sure that your ISO setting is high enough that the camera will select an aperture with sufficient depth-of-field, too.
• Concerts, stage performances. I shoot a lot of concerts with my 70-200mm f/2.8 lens, and have discovered that, when image stabilization is taken into account, a shutter speed of 1/180th second is fast enough to eliminate blur from hand-holding the camera with this lens, and also to avoid blur from the movement of all but the most energetic performers. I use Shutter-priority and set the ISO so the camera will select an aperture in the f/4-5.6 range.

Program AE Mode

Program mode (P) uses the camera’s built-in smarts to select the correct f/stop and shutter speed using a database of picture information that tells it which combination of shutter speed and aperture will work best for a particular photo. If the correct exposure cannot be achieved at the current ISO setting, the shutter speed or aperture indicator in the viewfinder will blink, indicating under- or overexposure. You can then boost or reduce the ISO to increase or decrease sensitivity.

The camera’s recommended exposure can be overridden if you want. Use the EV setting feature (described later, because it also applies to Tv and Av modes) to add or subtract exposure from the metered value. And, as I mentioned earlier in this chapter, you can change from the recommended setting to an equivalent setting (as shown in Table 4.1) that produces the same exposure but using a different combination of f/stop and shutter speed.

To accomplish this:

1. 1. Press the shutter release halfway to lock in the current base exposure or press the AE Lock button (*) on the back of the camera (in which case the * indicator will illuminate in the viewfinder to show that the exposure has been locked).
2. 2. If the camera cannot select an appropriate exposure, the shutter speed and aperture display will blink:
   • • Underexposure. The 30 shutter speed indicator will flash, along with the maximum (largest) aperture of the lens. (The exact number will vary, depending on which lens you are using.) To compensate, you must either use a higher ISO setting or provide additional illumination, such as electronic flash.
   • • Overexposure. The 8000 shutter speed indicator will flash, along with the minimum (smallest available) f/stop, such as f/16, f/22, or f/32, depending on the lens you are using. You can usually compensate for this by reducing the ISO speed to a lower setting. Your scene must be very bright indeed to trigger overexposure at a shutter speed of 1/8000th second and the lowest L (ISO 50 equivalent) sensitivity setting. But if you’re photographing, say, a blast furnace, and still have an overexposure situation, you can resort to a neutral-density filter or find some way to reduce the amount of illumination.
3. 3. Once an exposure is set, you can spin the Main Dial to change to a different combination of settings. Rotate left to select a longer shutter speed/smaller aperture, or to the right to choose a faster shutter speed/larger aperture.

Your adjustment remains in force for a single exposure; if you want to change from the recommended settings for the next exposure, you’ll need to repeat those steps.

When to use Program mode priority:

• When you’re in a hurry to get a grab shot. The camera will do a pretty good job of calculating an appropriate exposure for you, without any input from you.
• When you hand your camera to a novice. Set the camera to P, hand the camera to your friend, relative, or trustworthy stranger you meet in front of the Leaning Tower of Pisa, point to the shutter release button and viewfinder, and say, “Look through here, and press this button.”
• When no special shutter speed or aperture settings are needed. If your subject doesn’t require special anti- or pro-blur techniques, and depth-of-field or selective focus aren’t important, use P as a general-purpose setting. You can still make adjustments to increase/decrease depth-of-field or add/reduce motion blur with a minimum of fuss.

Flexible-Priority Mode

Flexible-priority (Fv) takes a little getting used to, because, at least among veteran photographers, the shooting modes P, Tv, Av, and Manual (discussed later) are ingrained in our workflow. Fv almost seems counterintuitive until you’ve used it a few times and the realization comes that it is probably the most intuitive shooting mode of all. Flexible-priority gives you all four modes with full control of the three legs of the exposure triangle, all within a single setting.

In a nutshell, Fv, by default, acts like Program AE with Auto ISO activated. That is, the camera selects shutter speed, aperture, and ISO setting for you automatically. But you can elect to manually specify any or all of those three, and the camera’s shooting mode magically transforms from P to Av, Tv, or Manual. With the mode set to Fv:

• Tv mode. In Fv mode, rotate the Quick Control Dial 1 until an orange icon representing the Main Dial appears next to the shutter speed. You can then rotate the Main Dial to manually select the shutter speed, and the aperture and ISO will continue to be changed automatically. In effect, you have Tv mode with Auto ISO. (See Figure 4.12.)
• Av mode. In Fv mode, rotate the Quick Control Dial 1 until an orange icon representing the Main Dial appears next to the aperture, then rotate the Main Dial to manually select the f/stop. The camera behaves just like it would in Av mode with Auto ISO.
• Manual mode. In Fv mode, rotate the Quick Control Dial 1 to the shutter speed and aperture icons and choose a manual setting for each. Now the camera acts as if it were in Manual exposure mode with shutter speed, and the aperture and ISO will continue to be changed automatically. In effect, you have Tv mode with Auto ISO.
• Fixed ISO. If you want to disable Auto ISO in Fv mode, rotate the Quick Control Dial 1 to highlight the ISO icon and select a fixed ISO value of your choice.
• Exposure compensation. Highlight the exposure scale at the bottom of the screen and rotate the Main Dial to add or subtract exposure compensation.

Figure 4.12 An exposure scale is shown at the bottom of the display.

Manual Exposure Mode

Part of being an experienced photographer comes from knowing when to rely on your camera’s automation (including Scene Intelligent Auto or P mode), when to go semi-automatic (with Tv or Av), and when to set exposure manually (using M). Some photographers actually prefer to set their exposure manually most of the time, as the camera will be happy to provide an indication of when its metering system judges your settings provide the proper exposure, using the analog exposure scale at the bottom of the display (see Figure 4.12) and on the status LCD panel of the R5.

Manual exposure can come in handy in some situations. You might be taking a silhouette photo and find that none of the exposure modes or EV correction features give you exactly the effect you want. For example, when I shot the ballet dancer in Figure 4.13 in front of a mostly dark background highlighted by an illuminated curtain off to the right, there was no way any of my camera’s exposure modes would be able to interpret the scene the way I wanted to shoot it, even with Spot metering, which didn’t have a narrow enough field-of-view from my position. So, I took a couple test exposures, and set the exposure manually using the exact shutter speed and f/stop I needed. You might be working in a studio environment using multiple flash units. The additional flash are triggered by slave devices (gadgets that set off the flash when they sense the light from another flash, or, perhaps from a radio or infrared remote control). Your camera’s exposure meter doesn’t compensate for the extra illumination, and can’t interpret the flash exposure at all, so you need to set the aperture manually.

Figure 4.13 Manual exposure allows selecting both f/stop and shutter speed, especially useful when you’re experimenting, as with this shot of ballet dancers.

Because, depending on your proclivities, you might not need to set exposure manually very often, you should still make sure you understand how it works. Fortunately, the camera makes setting exposure manually very easy. Just use the MODE dial to select Manual exposure, then turn the Main Dial to set the shutter speed, and the QCD-1 to adjust the aperture. Press the shutter release halfway or press the AE Lock (*) button, and the exposure scale in the viewfinder shows you how far your chosen setting diverges from the metered exposure.

If you activate ISO Auto, you can add or subtract exposure compensation. Just tap the exposure scale at the bottom of the touch screen, use the Quick Control screen’s Exposure Compensation function in the graphical screen, or use the Exposure Compensation/AEB entry in the Shooting 2 menu.

When to use Manual exposure:

• When working in the studio. If you’re working in a studio environment, you generally have total control over the lighting and can set exposure exactly as you want. The last thing you need is for the camera to interpret the scene and make adjustments of its own. Use M and the shutter speed, aperture, and (as long as you don’t use ISO-Auto) ISO setting are totally up to you.
• When using non-dedicated flash. External Canon-dedicated flash units are cool, but if you’re working with a non-compatible flash unit, particularly studio flash plugged into a PC/X adapter mounted on the hot shoe, the camera has no clue about the intensity of the flash, so you’ll have to dial in the appropriate aperture and shutter speed manually.
• If you’re using a hand-held light meter. The appropriate aperture, both for flash exposures and shots taken under continuous lighting, can be determined by a hand-held light meter, flash meter, or combo meter that measures both kinds of illumination. With an external meter, you can measure highlights, shadows, backgrounds, or additional subjects separately, and use Manual exposure to make your settings.
• When you want to outsmart the metering system. Your camera’s metering system is “trained” to react to unusual lighting situations, such as backlighting, extra-bright illumination, or low-key images with murky shadows. In many cases, it can counter these “problems” and produce a well-exposed image. But what if you don’t want a well-exposed image? Manual exposure allows you to produce silhouettes in backlit situations, wash out all the middle tones to produce a luminous look, or underexpose to create a moody or ominous dark-toned photograph.

Adjusting Exposure with ISO Settings

Another way of adjusting exposures is by changing the ISO sensitivity setting. Sometimes photographers forget about this option, because the common practice is to set the ISO once for a particular shooting session (say, at ISO 100 or 200 for bright sunlight outdoors, or ISO 800 when shooting indoors) and then forget about it. ISOs higher than ISO 100 or 200 are seen as “bad” or “necessary evils.” However, changing the ISO is a valid way of adjusting exposure settings, particularly with the Canon EOS R5/R6, which produces good results at ISO settings that create grainy, unusable pictures with some other camera models.

Indeed, I find myself using ISO adjustment as a convenient alternate way of adding or subtracting EV when shooting in Manual mode, and as a quick way of choosing equivalent exposures when in Auto or semi-automatic modes. For example, I’ve selected a Manual exposure with both f/stop and shutter speed suitable for my image using, say, ISO 200. I can change the exposure in one-third-stop increments by pressing the M-Fn button on top of the camera, highlighting ISO with the QCD-1, and then spinning the Main Dial one click at a time. The difference in image quality/noise at the base setting of ISO 200 is negligible if I dial in ISO 100 to reduce exposure a little or change to ISO 400 to increase exposure. I keep my preferred f/stop and shutter speed, but still adjust the exposure.

Or, perhaps, I am using Tv mode and the metered exposure at ISO 200 is 1/500th second at f/11. If I decide on the spur of the moment I’d rather use 1/500th second at f/8, I can press the M-Fn button, select ISO with the QCD-1, and spin the Main Dial to switch to ISO 100. Of course, it’s a good idea to monitor your ISO changes, so you don’t end up at ISO 1600 accidentally. ISO settings can, of course, also be used to boost or reduce sensitivity in particular shooting situations.

When not using Scene Intelligent Auto (which sets ISO automatically), the camera can set ISO speeds manually for stills. (In video mode, Auto ISO must be used in all modes except Manual exposure.) The ISO Speed Settings entry in the Shooting 2 menu allows you to specify what speeds are available and how they are used:

• ISO Speed. This scale allows you to choose from the enabled ISO speeds, plus Auto, using a sliding scale that can be adjusted using the QCD-1, the Multi-controller, or the touch screen. Pressing the INFO button when the scale is visible activates Auto.
• Range for Stills. You can specify the minimum and maximum ISO sensitivity available, including “expanded” settings such as Low (ISO 50 equivalent) and H (ISO 204,800 equivalent). I find myself using this feature frequently to keep me from accidentally switching to a setting I’d rather not use (or need to avoid). For example, at concerts I may switch from ISO 1600 to 6400 as the lighting changes, and I set those two values as my minimum or maximum. Outdoors in daylight, I might prefer to lock out ISO values lower than ISO 100 or higher than ISO 800.

• Auto Range. This is the equivalent “safety net” for Auto ISO operation. You can set the minimum no lower than ISO 100 and the maximum to ISO 25,600 (R5)/ISO 102,400 (R6), and no further. Use this to apply your own “smarts” to the Auto ISO setting.
• Minimum Shutter Speed. You can choose whether to allow the camera to select the slowest shutter speed used before Auto ISO kicks in. The idea here is that you’ll probably want to boost ISO sooner if you’re using a long lens with P and Av modes (in which the camera selects the shutter speed). If you specify, for example, a minimum shutter speed of 1/250th second, if P or Av mode needs a slower shutter speed for the proper exposure, it will boost ISO instead, within the range you’ve specified with Auto Range.

  This setting has two modes. In Auto mode, the camera decides when the shutter speed is too low. You can fine-tune this by choosing Slower or Faster on the scale (–3 to +3) that appears. Or, you can manually select the “trigger” shutter speed, from 1 second to 1/8000th second.

Dealing with Visual Noise

Visual image noise is that random grainy effect that some like to use as a special effect, but which, most of the time, is objectionable because it robs your image of detail even as it adds that “interesting” texture. Noise is caused by two different phenomena: high ISO settings and long exposures.

High ISO noise commonly first appears when you raise your camera’s sensitivity setting above ISO 3200. With Canon cameras, which are renowned for their good ISO noise characteristics, noise is usually fairly noticeable at ISO 6400 and above. At the H setting (ISO 102,400 equivalent [R5]/ISO 204,800 equivalent [R6]), noise is usually quite bothersome, which is why those lofty sensitivity ratings are disabled by default and must be activated with ISO expansion. This kind of noise appears as a result of the amplification needed to increase the sensitivity of the sensor. Because your sensor has twice as many green pixels as red and blue pixels, such noise is typically worse in areas that have red, blue, and magenta tones, because the green signals don’t have to be amplified as much to produce detail. While higher ISOs do pull details out of dark areas, they also amplify non-signal information randomly, creating noise.

A similar noisy phenomenon occurs during long time exposures, which allow more photons to reach the sensor, increasing your ability to capture a picture under low-light conditions. However, the longer exposures also increase the likelihood that some pixels will register random phantom photons, often because the longer an imager is “hot,” the warmer it gets, and that heat can be mistaken for photons. There’s also a special kind of noise that CMOS sensors like the one used in your camera are potentially susceptible to. With a CCD, the entire signal is conveyed off the chip and funneled through a single amplifier and analog-to-digital conversion circuit. Any noise introduced there is, at least, consistent. CMOS imagers, on the other hand, contain millions of individual amplifiers and A/D converters, all working in unison. Because all these circuits don’t necessarily process in precisely the same way all the time, they can introduce something called fixed-pattern noise into the image data.

Fortunately, Canon’s electronics geniuses have done an exceptional job minimizing noise from all causes in the camera. Even so, you might still want to apply the optional long exposure noise reduction that can be activated in the Shooting 4 menu. This type of noise reduction involves the camera taking a second, blank exposure, and comparing the random pixels in that image with the photograph you just took. Pixels that coincide in the two represent noise and can safely be suppressed. This noise reduction system, called dark frame subtraction, effectively doubles the amount of time required to take a picture, and is used only for exposures longer than one second. Noise reduction can reduce the amount of detail in your picture, as some image information may be removed along with the noise. So, you might want to use this feature with moderation. Some types of images don’t require noise reduction because the grainy pattern tends to blend into the overall scene.

To activate your camera’s long exposure noise reduction features, go to the Shooting 4 menu, as explained further in Chapter 11.

You can also apply noise reduction to a lesser extent using Photoshop or Canon Digital Photo Professional and when converting RAW files to some other format, using your favorite RAW converter, or an industrial-strength product like Noise Ninja (www.picturecode.com) to wipe out noise after you’ve already taken the picture.

Making EV Changes

Sometimes you’ll want more or less exposure than indicated by the camera’s metering system. Perhaps you want to underexpose to create a silhouette effect or overexpose to produce a high-key look. It’s easy to use the camera’s exposure compensation system to override the exposure recommendations, available in any non-automatic mode except Manual. There are three ways to make exposure value (EV) changes with the camera.

• Display/Quick Control Dial 1. When looking at the display, you can add/subtract exposure compensation +/– 3 stops by tapping the shutter release halfway (you don’t have to hold it down) and then rotating the QCD-1. Turn clockwise to add exposure, or counterclockwise to reduce exposure. The exposure scale at the bottom of the screen will indicate the amount of exposure compensation you’ve dialed in.
• Quick Control screen. With the graphic shooting information screen displayed (see Figure 4.14), press the Q button and navigate to the exposure scale. Then rotate the QCD-1. Rotate clockwise to add exposure, or counterclockwise to reduce exposure. (As always, you can use the touch screen to access these controls.) The exposure scale on the screen will indicate the amount of exposure compensation. You can also press SET when the scale is highlighted to view the full exposure compensation/autoexposure bracketing screen, discussed next.

Figure 4.14 Setting exposure compensation using the Quick Control screen.

• Shooting 2. Press the MENU button and rotate the Main Dial to select the Shooting 2 menu. Then highlight the Expo. Comp/AEB entry at the top. Press SET to access the screen shown in Figure 4.15. Then rotate the QCD-1 or slide a finger across the scale to select the amount of exposure compensation. The screen has helpful labels (Darker on the left and Brighter on the right) to make sure you’re adding/subtracting when you really want to.

  Note that this method has an advantage: you can specify automatic exposure bracketing from this screen just by rotating the Main Dial. I’ll explain bracketing in more detail next.

Figure 4.15 The full exposure compensation/auto exposure bracketing screen.

Bracketing Parameters

Bracketing is a method for shooting several consecutive exposures using different settings, as a way of improving the odds that one will be exactly right. Before digital cameras took over the universe, it was common to bracket exposures, shooting, say, a series of three photos at 1/125th second, but varying the f/stop from f/8 to f/11 to f/16. In practice, smaller than whole-stop increments were used for greater precision. Plus, it was just as common to keep the same aperture and vary the shutter speed, although in the days before electronic shutters, film cameras often had only whole-increment shutter speeds available. Figure 4.16 shows a typical bracketed series.

Today, cameras can bracket exposures much more precisely, and bracket white balance as well (using the WB Shift/Bkt entry found in the Shooting 3 menu and described in Chapter 11). While WB bracketing is sometimes used when getting color absolutely correct in the camera is important, autoexposure bracketing (AEB) is used much more often. When this feature is activated, the camera takes a series of shots, all at a different exposure value—one at the standard exposure, and the others with more or less exposure. In Av mode, the shutter speed will change, whereas in Tv mode, the aperture speed will change. The next sections will explain the parameters you can select.

Figure 4.16 In this bracketed series, you can see metered exposure (left), underexposure (center), and overexposure (right).

Number of Exposures

In the Custom Function 1 menu, under the Number of Bracketed Shots entry, you can elect to bracket 2, 3, 5, or 7 shots:

• 2 shots. The camera will capture one image at the base or standard exposure (which can be the metered exposure, or one that’s more or less than the metered exposure, as I’ll explain shortly). It then takes one additional shot that provides either more or less exposure relative to that “base” image. Rotate the QCD-1 to the right to specify more exposure for the second shot, or to the left to specify less exposure. The amount of additional/less exposure is determined by the increment you select. (Read on! I’ll tie all the parameters together in an upcoming section.)
• 3, 5, 7 shots. The camera captures one image at the base exposure, and then two, four, or six shots bracketed around that exposure, respectively. That translates to one over/one under at the 3-shot setting, two over/two under at the 5-shot setting, and three over/three under when using the 7-shot option.

Bracketing Sequence

Also in the Custom Function 1 menu, you’ll find a Bracketing Sequence entry, which allows you to specify the order in which the autoexposure bracketing series are exposed. Your choice will depend both on personal preference and what you intend to do with the bracketed shots. The options include:

• 0 - +: The exposure sequence is standard exposure, decreased exposure, increased exposure. With this default value, your base exposure will be captured and saved first on your memory card, followed by the progressively reduced exposure images, then the shots with increased exposure. You might prefer this order if you expect your standard exposure will be the preferred image and arranged first in the queue of each bracket set and want the alternate exposures to follow.
• - 0 +: The sequence is decreased exposure, standard exposure, increased exposure. This order is the most logical to use if you’re shooting with the intention to combine images using HDR (high dynamic range) techniques in your image editor or HDR utility. The final bracketed array is stored on your memory card starting with the most underexposed shot, and progressing to the best exposed, and then on to the overexposures. That makes it easy to use all of your bracketed shots in the HDR sequence, or to select only some of them to combine.
• + 0 -: This sequence is the inverse of the last one, progressing from increased exposure to standard exposure and decreased exposure. You might prefer this order if you expect to see your best exposures on the plus side of the exposure sequence and want them to be displayed first.

Bracketing Auto Cancel

The final relevant entry in the Custom Function 1 menu is Bracketing Auto Cancel. When you activate bracketing (in the Shooting 2 menu, described shortly), the camera continues to shoot bracketed exposures until you manually turn the bracket feature off, assuming you have this setting disabled. That’s a good thing. If you’re out shooting a series of bracketed exposures (especially for HDR), it’s convenient to have your bracket setting be “sticky” and still be active even if you turn your camera off. Some shooters like to bracket virtually everything and leave bracketing on routinely.

However, much of the time you’ll want to turn bracketing off, and you may not want to visit the Shooting 3 menu to deactivate it manually. Set Bracketing Auto Cancel to Enable in the Custom Function 1 menu, and bracketing is cancelled when you turn the camera off, change lenses, use the flash, or change memory cards. When this setting is set to Disable, bracketing remains in effect until you manually turn it off or use the flash. The flash still cancels bracketing, but your settings are retained.

Increment Between Exposures

You can choose the size of the jump between each of the bracketed exposures. To do that, you’ll need to visit the Expo. Comp./AEB entry in the Shooting 2 menu. There, you can select from +/- 1/3 to 3 full stops in 1/3-stop increments, by rotating the Main Dial. The next section provides instructions for producing a bracketed set.

Creating a Bracketed Set

Using autoexposure bracketing is trickier than it needs to be but has been made more flexible than with some earlier models. With the camera you are not limited to only three exposures (up to seven shots can be taken), and you can choose to bracket only overexposures or underexposures—a very useful improvement! Just follow these steps:

1. 1. Specify number of exposures and sequence. Choose the number of bracketed exposures you want and the sequence in which they will be shot in the Custom Function 1 menu, as described earlier.
2. 2. Activate the Expo. Comp./AEB screen. Press the MENU button and navigate to the Shooting 2 menu, where you’ll find the Expo. Comp./AEB option. Press SET to select this entry.
3. 3. Set the bracket range/increment. Rotate the Main Dial to spread out or contract the three bars to include the desired range and exposure increment you want to use. The wider the spread, the larger the increment and the larger the range of bracketed shots you’ll end up with. The Main Dial will allow you to set the bracket range to up to three stops on either side of the standard (middle) exposure.

   For example, in Figure 4.17, the left and right red highlighted bars are separated from the center bar by two marks, each representing 1/3rd stop, so the bracketing will produce one image at 2/3rds stop less than the zero point (the large center bar), one at the zero point, and one at 2/3rds stop more than that.

Figure 4.17 Use the Main Dial to set the bracket range.

1. 4. Adjust zero point/standard exposure. By default, the bracketing is zeroed around the center of the scale, which represents the correct exposure as metered by the camera. But you might want to have your three bracketed shots all biased toward overexposure or underexposure. Perhaps you feel that the metered exposure will be too dark or too light, and you want the bracketed shots to lean in the other direction. Use either QCD to move the bracket spread toward one end of the scale or the other. Figure 4.18 (top) shows the bracketing biased toward overexposure, while in Figure 4.18 (bottom), the zero point is clustered around underexposure.

Figure 4.18 Use the QCD-1 to bias the bracketing toward more or less exposure, and the Main Dial to set the bracket range.

1. 5. Confirm your choice. Press the SET button to enter the settings.
2. 6. Take your photo sequence. Press the shutter release to start capturing the bracketed sequence. The drive mode you select will determine when they are taken:
   • • Single shooting/Silent single shooting. Press the shutter release one time for each exposure in the sequence.
   • • High-speed continuous/Low-speed continuous/Silent continuous. You can hold down the shutter release and all the shots in the sequence will be exposed. The camera stops shooting when the series is complete.
   • • 10 sec./2 sec. self-timer modes. After the appropriate delay, all the shots in the sequence will be taken.
3. 7. Monitor your shots. As the images are captured, three indicators will appear on the exposure scale in the viewfinder, with one of them flashing for each bracketed photo, showing when the base exposure, underexposure, and overexposure are taken.
4. 8. Turn bracketing off when done. Bracketing remains in effect when the set is taken so you can continue shooting bracketed exposures until you use the electronic flash, turn off the camera, or return to the menu to cancel bracketing. That’s true even if you have set Bracketing Auto Cancel to Enable in the Custom Function 1 menu. If bracketing were actually auto canceled, you’d have to respecify bracketing for each sequence you took; instead, the camera remembers your bracketing settings until you cancel manually, or until you power down or begin to use electronic flash.

Working with HDR

High dynamic range (HDR) photography is quite the rage these days, and entire books have been written on the subject. It’s not really a new technique—film photographers have been combining multiple exposures for ages to produce a single image of, say, an interior room while maintaining detail in the scene visible through the windows.

Suppose you wanted to photograph a dimly lit room that had a bright window showing an outdoors scene. Proper exposure for the room might be on the order of 1/60th second at f/2.8 at ISO 200, while the outdoors scene probably would require f/11 at 1/400th second. That’s almost a 7 EV step difference (approximately 7 f/stops) and effectively beyond the dynamic range of any digital camera.

Until camera sensors gain much higher dynamic ranges (which may not be as far into the distant future as we think), special tricks like Auto Lighting Optimizer and HDR photography will remain basic tools. You can create in-camera HDR exposures or shoot HDR the old-fashioned way—with separate bracketed exposures that are later combined in a tool like Photomatix or Adobe’s Merge to HDR Pro image-editing feature. I’m going to show you how to use both.

The in-camera HDR feature is simple, flexible, and surprisingly effective in creating high dynamic range images. It’s also remarkably easy to use. Although it combines only three images to create a single HDR photograph, and it’s not always as good as the manual HDR method, it’s a lot faster.

Figure 4.19 shows you a typical situation in which you might want to use this setting. When the exposure is set for the interior of this covered bridge, the foliage surrounding it is overexposed (upper left). When the exposure is adjusted to produce detail in the foliage, the interior of the bridge goes dark (lower left). HDR allows combining the detail from multiple images—not just the two shown at left, but as many as you want, if you combine them manually (as I’ll show you later) to get the image shown at right.

Figure 4.19 HDR combined the two images at left to produce the final version at right.

Using HDR Mode

Here are some tips for using this feature:

• Use a tripod if possible. Because there may be some camera movement between the continuous shots, you’ll get better results if you mount the camera on a tripod.
• Moving objects may produce ghosts. In this case, there may be some subject motion between shots, producing “ghost” effects.
• Misalignment. If you don’t use a tripod, when Auto Image Align is activated, this mode does a good job of realigning your multiple images when they are merged. However, it can’t do a perfect job, particularly with repetitive patterns that are difficult for the camera’s “brains” to sort out. Some misalignment is possible.
• Shutter speeds vary. The camera brackets by adjusting the shutter speed within the increment range selected, even if you’re using Tv or M modes and have specified a shutter speed. Changing the f/stop while shooting an HDR photo alters the focus and possibly image size, and so is not compatible with HDR.
• Unwanted cropping. Because the processor needs to be able to shift each individual image slightly in any (or all) of four directions in Auto Image Align mode, it needs to crop the image slightly to trim out any non-image areas that result. Your final image will be slightly smaller than one shot in other modes.
• Weird colors. Some types of lighting, including fluorescent and LED illumination, “cycle” many times a second, and colors can vary between shots. You may not even notice this when single shooting, but it becomes more obvious when using any continuous shooting mode, including HDR mode. The combined images may have strange color effects.
• Limitations. Images are captured in JPEG format only, even if you’ve specified RAW or RAW+JPEG. Extended ISO speeds aren’t available, the flash will not fire during HDR capture, and Auto Exposure Bracketing is disabled. While you can use HDR mode if Auto Lighting Optimizer has been enabled, the camera will disable it while shooting your HDR images, then reenable it when you turn HDR mode off.
• The process takes time. Forget about firing off a large number of HDR shots in a row. After the camera captures its three images, it takes a few seconds to process them and save your final image. Be patient.

You can locate HDR Mode in the Shooting 5 menu. Press the SET button, and you’ll be taken to the menu shown in Figure 4.20. This menu has five entries:

• Adjust Dynamic Range. There are five choices in this entry. Select Disable HDR to turn HDR completely off. The others select the number of stops of dynamic range improvement the HDR feature will provide. Choose Auto to allow the camera to examine your scene and select an appropriate EV range. As you gain experience you might want to select the range yourself, in order to achieve a particular look. You can choose +/- 1, 2, or 3 EV.
• Effect. If you’ve worked with HDR utilities (such as Photomatix) in the past, you know that various parameters can be adjusted while combining HDR images to produce various effects. These include the amount of color saturation (the “richness” of the hues); the boldness of the edge transitions between portions of the image (producing mild to distinct outlines); the brightness of the resulting image; and contrast/tone. Various combinations of these settings produce what can only be called special effects. Select from what Canon terms Natural, Art Standard, Art Vivid, Art Bold, or Art Embossed. Note that these effects are added to the settings of any Picture Style currently in use.
• Continuous HDR. Choose 1 Shot Only if you plan to take just a single HDR exposure and want the feature disabled automatically thereafter, or Every Shot to continue using HDR mode for all subsequent exposures until you turn it off.
• Auto Image Align. HDR images are ideally produced with the camera on a tripod, in order to reduce the ghosting effects from a series of pictures that each aren’t perfectly aligned with the other. You can choose Enable to have the camera attempt to align all three HDR exposures or select Disable when using a tripod. The success of the automatic alignment will vary, depending on the shutter speed used (higher is better), and the amount of camera movement (less is better!).
• Save Source Images. When the camera has finished creating its HDR image from your three shots, you can choose to save all the images on your memory card (so you can manually combine them later or perform other manipulations using your image editor). Or, you can elect to save your final HDR image only. You might prefer that choice to save card space, reduce the number of images you won’t be using anyway, or if you’re shooting a lot of HDR and are confident that the camera’s results will suit your needs.

Figure 4.20 The HDR mode menu has five entries.

Figure 4.21 Top row (left to right): Natural, Art Standard, Art Vivid; bottom row: Art Bold, Art Embossed.

Bracketing and Merge to HDR

HDR photography was, for a while, an incredibly popular fad. Everywhere you looked there were overprocessed, garish HDR images that had little relationship to reality. I’ve been able to resist the temptation to overdo my landscape and travel photography (unlike the deliberately awful example I created for Figure 4.22). The phony-looking skies, the unnatural halos that appear at the edges of some objects, and the weird textures are usually a giveaway. My rule of thumb is that, if you can tell it’s HDR, it’s been done wrong—unless your intent was to show off what HDR can do.

The technique does have its uses, especially if done subtly, or as a special effect. That’s what I was looking for when I shot Alastair Greene, guitarist for the Alan Parsons Project for Figure 4.23. I wanted an edgy, poster-like quality, and so applied HDR liberally, but with the hope that the effect might not be evident on first glance.

Although the camera does have its built-in HDR feature, you can usually get much better, more tasteful results if you create your high dynamic range images manually. You can use a tool such as Photoshop’s Merge to HDR Pro feature, a stand-alone HDR utility, or a third-party Photoshop plug-in.

Figure 4.22 A deliberately overcooked HDR photo.

Figure 4.23 In this case, HDR added a desired poster-like effect.

When you’re using Merge to HDR Pro in Adobe Photoshop (similar functions are available in other programs, including the Mac/PC utility Photomatix [www.hdrsoft.com; free to try, $39–$99 to buy, depending on the version you select]) and Aurora HDR (www.skylum.com, $69), you’d take and combine several pictures. As I mentioned earlier, one would be exposed for the shadows, one for the highlights, and perhaps one for the midtones. Then, you’d use the Merge to HDR command (or the equivalent in other software) to combine all of the images into one HDR image that integrates the well-exposed sections of each version. You can use the camera’s bracketing feature to produce those images.

The next steps show you how to combine the separate exposures into one merged high dynamic range image. The sample images in Figure 4.24 show the results you can get from a three-shot (manually) bracketed sequence. The images should be as identical as possible, except for exposure. So, as with HDR mode, it’s a good idea to mount the camera on a tripod, use a remote release, and take all the exposures at once. Just follow these steps:

1. 1. Set up the camera. Mount the camera on a tripod.
2. 2. Choose an f/stop and Av mode. Select an aperture that will provide a correct exposure at your initial settings for the series of bracketed shots. And then leave this adjustment alone! You don’t want the aperture to change for your series, as that would change the depth-of-field, and, subtly, the size of some elements of the image as they move more or less out of focus. You want the camera to adjust exposure only using the shutter speed.

Figure 4.24 Three bracketed photos should look like this (left). The finished image is shown at right.

1. 3. Choose manual focus. You don’t want the focus to change between shots, so set the camera to manual focus, and carefully focus your shot.
2. 4. Choose RAW exposures. Set the camera to take RAW files, which will give you the widest range of tones in your images.
3. 5. Set up your bracketed set. Use the instructions earlier in this chapter to set the number of bracketed images you take, and the increment between them. After you’ve created your first few manual HDR photos, you’ll learn to judge what increment is best (larger isn’t always better). However, the more shots you have to work with, the better your results can be.
4. 6. Take your photos. With the camera in continuous shooting mode, press the button on the remote (or carefully press the shutter release or use the self-timer) and take the set of bracketed exposures.
5. 7. Continue with the Merge to HDR Pro steps listed next. You can also use a different program, such as Photomatix, if you know how to use it.

The next steps show you how to combine the separate exposures into one merged high dynamic range image.

1. 1. Copy your images to your computer. If you use an application to transfer the files to your computer, make sure it does not make any adjustments to brightness, contrast, or exposure. You want the real raw information for Merge to HDR Pro to work with.
2. 2. Activate Merge to HDR Pro. Choose File > Automate > Merge to HDR Pro.
3. 3. Select the photos to be merged. Use the Browse feature to locate and select your photos to be merged. You’ll note a checkbox that can be used to automatically align the images if they were not taken with the camera mounted on a rock-steady support. This will adjust for any slight movement of the camera that might have occurred when you changed exposure settings.
4. 4. Choose parameters (optional). The first time you use Merge to HDR Pro, you can let the program work with its default parameters. Once you’ve played with the feature a few times, you can read the Adobe help files and learn more about the options than I can present in this non-software-oriented camera guide.
5. 5. Click OK. The merger begins.
6. 6. Save. Once HDR merge has done its thing, save the file to your computer.

What if you don’t have the opportunity, inclination, or skills to create several images at different exposures, as described? If you shoot in RAW format, you can still use Merge to HDR, working with a single original image file. What you do is import the image into Photoshop several times, using Adobe Camera Raw to create multiple copies of the file at different exposure levels.

For example, you’d create one copy that’s too dark, so the shadows lose detail, but the highlights are preserved. Create another copy with the shadows intact and allow the highlights to wash out. Then, you can use Merge to HDR to combine the two and end up with a finished image that has the extended dynamic range you’re looking for. (This concludes the image-editing portion of the chapter. We now return you to our alternate sponsor: photography.)

Fixing Exposures with Histograms

While you can often recover poorly exposed photos in your image editor, your best bet is to arrive at the correct exposure in the camera, minimizing the tweaks that you have to make in post-processing. However, you can’t always judge exposure just by simply looking at the preview image on your camera’s display before the shot is made, nor the review image in Playback. Ambient light may make the monitor difficult to see, and the brightness level you’ve set for the monitor and viewfinder in the Set-up menu can affect the appearance of the image.

Instead, you can use a histogram, which is a chart shown on the camera’s display that shows the number of tones that have been captured at each brightness level. Histograms are available in real time on your display as you shoot and in the review image during playback, but they are available only when enabled. I’ll show you how to enable histograms and select from among the various options available for histograms in Chapter 13. To view histograms in shooting mode or playback mode, press the INFO button until a screen with the histogram appears.

Histograms come in various flavors. Photographers are generally concerned only with two types: a brightness or luminance histogram, which deals only with the relative overall intensity of the tones in the image (see Figure 4.25, top), and a color histogram that displays the intensity of each individual color channel in a particular color space (see Figure 4.25, bottom). Photographers most often work with an RGB histogram that displays values for red, green, and blue pixels in an image, but other varieties exist, such as CMYK (for cyan, magenta, yellow, and black hues) and HSL/HSV (hue, saturation, and lightness/value), which are alternate ways of representing the RGB color space.

To get you up to speed with histograms, the next few sections will deal only with the brightness/luminance histogram variety.

Figure 4.25 Brightness histogram (top), RGB histogram (bottom).

Tonal Range

Histograms help you adjust the tonal range of an image, the span of dark to light tones, from a complete absence of brightness (black) to the brightest possible tone (white), and all the middle tones in between. Because all values for tones fall into a continuous spectrum between black and white, it’s easiest to think of a photo’s tonality in terms of a black-and-white or grayscale image, even though you’re capturing those tones in three separate color layers of red, green, and blue.

Figure 4.26 A tonal range from black (left) to white (right) and all the gray values in between.

Because your images are digital, the tonal “spectrum” isn’t really continuous: it’s divided into discrete steps that represent the different tones that can be captured. Figure 4.26 may help you understand this concept. The gray steps shown range from 100 percent gray (black) at the left, to 0 percent gray (white) at the right, with 20 gray steps in all (plus white).

Along the bottom of the chart are the digital values from 0 to 255 recorded by your sensor for an image with 8 bits per channel. (8 bits of red, 8 bits of green, and 8 bits of blue equal a 24-bit, full-color image.) Any black captured would be represented by a value of 0, the brightest white by 255, and the midtones would be clustered around the 128 marker. The actual information captured may be “finer” and record say, 0 to 4,094 for an image captured when the camera is set to 14 bits per channel for a RAW file (see Chapter 11 for more detail on that option).

Grayscale images (which we call black-and-white photos) are easy to understand. Or, at least, that’s what we think. When we look at a black-and-white image, we think we’re seeing a continuous range of tones from black to white, and all the grays in between. But, that’s not exactly true. The blackest black in any photo isn’t a true black, because some light is always reflected from the surface of the print, and if viewed on a screen, the deepest black is only as dark as the least-reflective area a computer monitor can produce. The whitest white isn’t a true white, either, because even the lightest areas of a print absorb some light (only a mirror reflects close to all the light that strikes it), and, when viewing on a computer monitor, the whites are limited by the brightness of the display’s LCD or LED picture elements. Lacking darker blacks and brighter, whiter whites, that continuous set of tones doesn’t cover the full grayscale tonal range.

The full scale of tones becomes useful when you have an image that has large expanses of shades that change gradually from one level to the next, such as areas of sky, water, or walls. Think of a picture taken of a group of campers around a campfire. Since the light from the fire is striking them directly in the face, there aren’t many shadows on the campers’ faces. All the tones that make up the features of the people around the fire are compressed into one end of the brightness spectrum—the lighter end.

Yet, there’s more to this scene than faces. Behind the campers are trees, rocks, and perhaps a few animals that have emerged from the shadows to see what is going on. These are illuminated by the softer light that bounces off the surrounding surfaces. If your eyes become accustomed to the reduced illumination, you’ll find that there is a wealth of detail in these shadow images.

This campfire scene would be a nightmare to reproduce faithfully under any circumstances. If you are an experienced photographer, you are probably already wincing at what is called a high-contrast lighting situation. Some photos may be high in contrast when there are fewer tones, and they are all bunched up at limited points in the scale. In a low-contrast image, there are more tones, but they are spread out so widely that the image looks flat. Your digital camera can show you the relationship between these tones using a histogram.

Histogram Basics

Your camera’s histograms are a simplified display of the numbers of pixels at each of 256 brightness levels, producing an interesting “mountain range” shape in the graph. Although separate charts may be provided for brightness and the red, green, and blue channels, when you first start using histograms, you’ll want to concentrate on the brightness histogram.

Each vertical line in the graph represents the number of pixels in the image for each brightness value, from 0 (black) on the left to 255 (white) on the right. The vertical axis measures that number of pixels at each level.

Although histograms are most often used to fine-tune exposure, you can glean other information from them, such as the relative contrast of the image. Figure 4.27, top, shows a generic histogram of an image having normal contrast. In such an image, most of the pixels are spread across the image, with a healthy distribution of tones throughout the midtone section of the graph. That large peak at the right side of the graph represents all those light tones in the sky. A normal-contrast image you shoot may have less sky area, and less of a peak at the right side, but notice that very few pixels hug the right edge of the histogram, indicating that the lightest tones are not being clipped because they are off the chart.

Figure 4.27 Top: This image has fairly normal contrast, even though there is a peak of light tones at the right side representing the sky. Center: This low-contrast image has all the tones squished into one section of the grayscale. Bottom: A high-contrast image produces a histogram in which the tones are spread out.

With a lower-contrast image, like the one shown in Figure 4.27, center, the basic shape of the previous histogram will remain recognizable, but gradually will be compressed together to cover a smaller area of the gray spectrum. The squished shape of the histogram is caused by all the grays in the original image being represented by a limited number of gray tones in a smaller range of the scale.

Instead of the darkest tones of the image reaching into the black end of the spectrum and the whitest tones extending to the lightest end, the blackest areas of the scene are now represented by a light gray, and the whites by a somewhat lighter gray. The overall contrast of the image is reduced. Because all the darker tones are actually a middle gray or lighter, the scene in this version of the photo appears lighter as well.

Going in the other direction, increasing the contrast of an image produces a histogram like the one shown in Figure 4.27, bottom. In this case, the tonal range is now spread over the entire width of the chart, but, except for the bright sky, there is not much variation in the middle tones; the mountain “peaks” are not very high. When you stretch the grayscale in both directions like this, the darkest tones become darker (that may not be possible) and the lightest tones become lighter (ditto). In fact, shades that might have been gray before can change to black or white as they are moved toward either end of the scale.

The effect of increasing contrast may be to move some tones off either end of the scale altogether, while spreading the remaining grays over a smaller number of locations on the spectrum. That’s exactly the case in the example shown. The number of possible tones is smaller, and the image appears harsher.

Understanding Histograms

The important thing to remember when working with the histogram display in your camera is that changing the exposure does not change the contrast of an image. The curves illustrated in the previous three examples remain exactly the same shape when you increase or decrease exposure. I repeat: The proportional distribution of grays shown in the histogram doesn’t change when exposure changes; it is neither stretched nor compressed. However, the tones as a whole are moved toward one end of the scale or the other, depending on whether you’re increasing or decreasing exposure. You’ll be able to see that in some illustrations that follow.

So, as you reduce exposure, tones gradually move to the black end (and off the scale), while the reverse is true when you increase exposure. The contrast within the image is changed only to the extent that some of the tones can no longer be represented when they are moved off the scale.

To change the contrast of an image, you must do one of four things:

• Change the camera’s contrast setting using the menu system. You’ll find these adjustments in your camera’s Picture Styles options in the Shooting 3 menu, as explained in Chapter 11.
• Use your camera’s shadow-tone and highlight “boosters.” Auto Lighting Optimizer and Highlight Tone Priority, also discussed in Chapter 11, can help you adjust contrast.
• Alter the contrast of the scene itself, for example, by using a fill light or reflectors to add illumination to shadows that are too dark.
• Attempt to adjust contrast in post-processing using your image editor or RAW file converter. You may use features such as Levels or Curves (in Photoshop, Photoshop Elements, and many other image editors) or work with HDR software to cherry-pick the best values in shadows and highlights from multiple images.

Of the four of these, the third—changing the contrast of the scene—is the most desirable, because attempting to fix contrast by fiddling with the tonal values is unlikely to be a perfect remedy. However, adding a little contrast can be successful because you can discard some tones to make the image more contrasty. However, the opposite is much more difficult. An overly contrasty image rarely can be fixed because you can’t add information that isn’t there in the first place.

What you can do is adjust the exposure so that the tones that are already present in the scene are captured correctly. Figure 4.28, top, shows the histogram for an image that is badly underexposed. You can guess from the shape of the histogram that many of the dark tones to the left of the graph have been clipped off. There’s plenty of room on the right side for additional pixels to reside without having them become overexposed. So, you can increase the exposure (either by changing the f/stop or shutter speed, or by adding an EV value) to produce the corrected histogram shown in Figure 4.28, center.

Figure 4.28 Top: A histogram of an underexposed image may look like this. Center: Adding exposure will produce a histogram like this one. Bottom: A histogram of an overexposed image will show clipping at the right side.

Conversely, if your histogram looks like the one shown in Figure 4.28, bottom, with bright tones pushed off the right edge of the chart, you have an overexposed image, and you can correct it by reducing exposure. In addition to the histogram, the camera has its Highlights option, which, when activated, shows areas that are overexposed with flashing tones (often called “blinkies”) in the review screen. Depending on the importance of this “clipped” detail, you can adjust exposure or leave it alone. For example, if all the dark-coded areas in the review are in a background that you care little about, you can forget about them and not change the exposure, but if such areas appear in facial details of your subject, you may want to make some adjustments.

In working with histograms, your goal should be to have all the tones in an image spread out between the edges, with none clipped off at the left and right sides. Underexposing (to preserve highlights) should be done only as a last resort, because retrieving the underexposed shadows in your image editor will frequently increase the noise, even if you’re working with RAW files. A better course of action is to expose for the highlights, but, when the subject matter makes it practical, fill in the shadows with additional light, using reflectors, fill flash, or other techniques rather than allowing them to be seriously underexposed.

A traditional technique for optimizing exposure is called “expose to the right” (ETTR), which involves adding exposure to push the histogram’s curve toward the right side but not far enough to clip off highlights. The rationale for this method is that extra shadow detail will be produced with a minimum increase in noise, especially in the shadow areas. It’s said that half of a digital sensor’s response lies in the brightest areas of an image, and so require the least amount of amplification (which is one way to increase digital noise). ETTR can work, as long as you’re able to capture a satisfactory amount of information in the shadows.

Exposing to the Right

It’s easier to understand exposing to the right if you mentally divide the histogram into fifths (unfortunately, the camera’s histogram uses quarters instead). And, for the sake of simplicity and smaller numbers, assume you’re shooting in 14-bit RAW. Any 14-bit image can record a maximum of 16,383 different tones per channel. However, each fifth of the histogram does not encompass 3,277 tones (one-fifth of 16,383).

Instead, the right-most fifth, the highlights, shown in Figure 4.29, accounts for 8,192 different captured tones. Moving toward the left, the next fifth represents 4,096 levels, followed by 2,048 levels, 1,024 levels, and, in the left-most section where the deepest shadows reside, only 512 different tones are captured. When processing your RAW file, there are only 512 tones to recover in the shadows, which is why boosting/amplifying them increases noise. (The effect is most noticeable in the red and blue channels; your sensor’s Bayer array has twice as many green-sensitive pixels as red or blue.) Instead, you want to add exposure—as long as you don’t push highlights off the right edge of the histogram—to brighten the shadows. Because there are 8,192 tones available in the highlights, even if the RAW image looks overexposed, it’s possible to use your RAW converter’s Exposure slider (such as the one found in Adobe Camera Raw) to bring back detail captured in that surplus of tones in the highlights. This procedure is the exact opposite of what was recommended for film of the transparency variety—it was fairly easy to retrieve detail from shadows by pumping more light through them when processing the image, while even small amounts of extra exposure blew out highlights. (Note: I’ve rounded the numbers a bit for simplicity.) You’ll often find that the range of tones in your image is so great that there is no way to keep your histogram from spilling over into the left and right edges, costing you both highlight and shadow detail. Exposing to the right may not work in such situations. A second school of thought recommends reducing exposure to bring back the highlights, or “exposing to the left.” You would then attempt to recover shadow detail in an image editor, using tools like Adobe Camera Raw’s Exposure slider. But remember, above all, that this procedure will also boost noise in the shadows, and so the technique should be used with caution. In most cases, exposing to the right is your best bet.

Figure 4.29 Tones are not evenly allocated throughout a histogram.

Dealing with Channels

The more you work with histograms, the more useful they become. One of the first things that histogram veterans notice is that it’s possible to overexpose one channel even if the overall exposure appears to be correct. For example, flower photographers soon discover that it’s really, really difficult to get a good picture of a red rose, like the one shown at left in Figure 4.30. The exposure looks okay—but there’s no detail in the rose’s petals. Looking at the histogram (see Figure 4.30, right) shows why: the red channel is blown out. If you look at the red histogram, there’s a peak at the right edge that indicates that highlight information has been lost. In fact, the green channel has been blown, too, and so the green parts of the flower also lack detail. Only the blue channel’s histogram is entirely contained within the boundaries of the chart, and, on first glance, the white luminance histogram at top of the column of graphs seems fairly normal.

Figure 4.30 It’s common to lose detail in bright red flowers because the red channel becomes overexposed even when the other channels are properly exposed (left). The RGB histograms show that both the red and green channels are overexposed, with tones extending past the right edge of the chart (right).

Any of the primary channels—red, green, or blue—can blow out all by themselves, although bright reds seem to be the most common problem area. More difficult to diagnose are overexposed tones in one of the “in-between” hues on the color wheel. Overexposed yellows (which are very common) will be shown by blowouts in both the red and green channels. Too-bright cyans will manifest as excessive blue and green highlights, while overexposure in the red and blue channels reduces detail in magenta colors. As you gain experience, you’ll be able to see exactly how anomalies in the RGB channels translate into poor highlights and murky shadows.

The only way to correct for color channel blowouts is to reduce exposure. As I mentioned earlier, you might want to consider filling in the shadows with additional light to keep them from becoming too dark when you decrease exposure. In practice, you’ll want to monitor the red channel most closely, followed by the blue channel, and slightly decrease exposure to see if that helps. Because of the way our eyes perceive color, we are more sensitive to variations in green, so green channel blowouts are less of a problem, unless your main subject is heavily colored in that hue. If you plan on photographing a frog hopping around on your front lawn, you’ll want to be extra careful to preserve detail in the green channel, using bracketing or other exposure techniques outlined in this chapter.