Chapter 10: Choosing Lenses and Accessories
Just as the human eye is the artistic lens for the photographer, the camera lens interprets a scene for the camera, and ultimately, for your images. Your choice of lens is like the choice of a brush is to an artist. The more you know about lenses, the better your chances of selecting the right lens for the subject. Not surprisingly, Canon refers to its stable of more than 60 lenses as The Eyes of EOS.
As you evaluate lenses that you may want to buy, know that the higher the lens quality, the better the image you’ll get with the 70D. High-quality lenses capture and retain excellent image detail even as you enlarge images for printing. As you buy new lenses, remember that you are building a system that will last for years — much longer than the camera body.
The EF 180 f/3.5L Macro USM lens provided the reach I needed to photograph this butterfly without disturbing it. Exposure: ISO 200, f/5.62, 1/800 second, -2/3 exposure compensation.
Lens Choices for the 70D
With more than 60 lenses available from Canon and many more available from third-party manufacturers, you can find a lens for virtually any shooting situation. While there are lenses aplenty, many of the best lenses carry high price tags. If you’re new to photography or shooting with a Canon camera, I recommend planning lens purchases with the goal of gradually building a system that meets your shooting needs, while maximizing the money you have to spend on lenses.
For new photographers who have not settled on a specialty area yet, a good rule of thumb is to begin by buying two lenses that cover the focal range from wide angle to telephoto. With those two lenses as the foundation of your system, you can shoot 90 percent of the scenes and subjects that you’ll encounter.
Because it’s likely you’ll use these lenses most often, they should be high quality. High-quality lenses produce images with snappy contrast and excellent sharpness, have low color fringing and distortion, provide even illumination across the frame, and are fast enough to allow shooting in low-light scenes.
A fast lens is generally one with a maximum aperture of f/2.8 or wider. If the lens has Image Stabilization, you gain even more low-light shooting flexibility.
When I switched to Canon almost 10 years ago, my first Canon lenses were the EF 24-70mm f/2.8L USM and EF 70-200mm f/2.8L IS USM. These high-quality lenses covered the focal range of 24mm to 200mm on a full-frame camera. Today, I still use these lenses most often for everyday shooting. Because I shoot with a variety of Canon EOS cameras, I also know that I can use these lenses on any EOS camera body and get beautiful images.
For a videographer, EF lenses open doors to creative techniques that are impossible with traditional video cameras and lenses. EF lenses offer a shallow depth of field with a large aperture that often cannot be achieved with video lenses. And with fisheye lenses that have a 180-degree field of view, videos can provide views wider than can be seen by the viewer’s eye. Likewise, high-magnification filming with a macro lens offers a view into tiny worlds. EF lenses enable videographers to record with a controlled perspective not offered by traditional video cameras.
Image courtesy of Canon
10.1 The EF 70-200mm f/2.8L IS II USM is a good starting point for building a lens system.
If you bought the 70D as a kit with either the EF-S 18-55mm f/3.5-5.6 IS STM or the EF-S 18-135mm f/3.5-5.6 IS STM lens, you already know that both lenses provide a good focal range for everyday shooting of still images and video. Of course, the 18-135mm lens provides a greater focal length range, and that makes it more versatile than the 18-55mm lens, but both are quite capable lenses. These lenses have the STM designation for Canon’s stepping motor that provides fast, quiet focusing.
If you have the 18-55mm lens, then your next purchase might be a telephoto lens or a macro telephoto lens that not only enables wonderful macro shots, but also serves as a great lens for portraits and still-life subjects.
Types of Lenses
Canon uses the designation EF (electro-focus) for lenses, and it simply identifies the type of mount the lens has. The EF lens mount provides quick mounting and removal of the lens, as well as providing communication between the lens and the camera body. The EF mount is fully electronic and resists abrasion, shock, and play. When you mount a lens, it does an automatic self-check and alerts you to any malfunction. And if you use lens accessories such as lens extenders, the exposure compensation is automatically calculated.
Many lenses also carry the USM designation, which stands for ultrasonic motor. USM lenses include a built-in motor powered by the camera, and the motor provides exceptionally fast focus. USM lenses also use electronic vibrations created by piezoelectric ceramic elements to provide quick and quiet focusing action with almost instantaneous starts and stops. Lenses with a ring-type ultrasonic motor offer full-time manual focusing without needing to switch the lens to Manual focus ( 
). This is offered on large-aperture and super-telephoto lenses.
Lenses are categorized by whether they zoom to different focal lengths or have fixed focal lengths (known as prime lenses). There are three main categories: Wide-angle, normal, and telephoto. Macro lenses are either normal or telephoto, with the added advantage of their close focusing capability.
Another important lens distinction for the 70D is that it’s compatible with both EF- and EF-S-mount lenses. The EF lens mount is compatible across all Canon EOS cameras, regardless of image sensor size and camera type, whether digital or film. However, EF-S lenses are specially designed to project a smaller image circle to the image sensor. EF-S lenses can be used only on cameras with cropped sensors, such as the 70D, T5i, and 7D. Because the rear element on EF-S lenses protrudes back into the camera body, they can’t be used on full-frame cameras.
This also factors into how you build your lens system. As you buy lenses, think about whether you want those that are compatible with all Canon digital SLR cameras, or only those with the cropped sensor. As your photography career progresses, you’ll most likely buy a second, backup camera body or move from the 70D to another EOS camera body. If your next EOS camera body has a full 35mm frame sensor, you’ll want the lenses you’ve already acquired to be compatible with it, which means buying the EF-mount lenses. If you have EF-S lenses on hand in this situation, you can sell them, of course.
Understanding the focal-length multiplier
An important lens consideration for the 70D is that the camera has an APS-C-size image sensor. APS-C is simply a designation that indicates that the image sensor is 60 percent of the size of a traditional full 35mm frame. Because the image sensor is smaller than the 35mm frame, when you use an EF lens on the 70D, the smaller image sensor takes in less of the scene than a full-frame size image sensor would.
This means the effective angle of view for Canon EF lenses that you use on the 70D is reduced by a factor of 1.6X at any given focal length. For example, a 100mm lens is equivalent to a 160mm lens on the 70D. Likewise, a 50mm lens is the equivalent of using an 80mm — a short telephoto lens on the 70D.
10.2 The difference in image size between a full-frame sensor and the smaller 70D (in color).
With the cropped sensor on the 70D, an EF lens’s focal length must be multiplied by 1.6 to determine its actual focal length on the 70D. However, in everyday conversation, photographers refer to EF lenses by their focal length on a non-cropped (full 35mm frame) camera.
Just from the previous examples, you can see that you get extra reach from your lenses thanks to the focal-length multiplication factor. With telephoto lenses, it effectively increases the lens’s focal length (although technically the focal length doesn’t change). Given that telephoto lenses are more expensive than other lenses, you can buy a shorter and less expensive telephoto lens and get 1.6X more magnification at no extra cost. Also, because the smaller sensor uses the center (or sweet spot) of the lens, you get high sharpness and less chromatic aberration.
Where there is an upside, there is surely a downside. The downside of the focal-length multiplication factor is that wide-angle lenses include less of the scene than they do on full-frame cameras. This is because the focal length is magnified by 1.6. However, you can get a EF-S 10-22mm f/3.5-4.5 USM for an affordable price and get a true wide-angle view.
As you think about the focal-length multiplier effect on telephoto lenses, it seems reasonable to assume that the focal-length multiplier would produce the same depth of field that a longer lens — the equivalent focal length — does. That isn’t the case, however. Although an 85mm lens on a full 35mm-frame camera is equivalent to a 136mm lens on the 70D, the depth of field on the 70D matches the 85mm lens, not a 136mm lens. This depth of field principle also holds true for enlargements. The depth of field in the print is shallower for the longer lens on a full-frame camera than it is for the 70D.
Zooms
Zoom lenses offer variable focal lengths in a single lens so that when you adjust the zoom ring, you bring the subject closer to you or move it farther away. Without question, zoom lenses are practical and convenient. For example, if you need lenses to cover a wide focal range, then the EF 16-35mm f/2.8L II USM and EF 70-200mm f/2.8L IS II USM (or a similar combination of two zoom lenses) would meet your goal. With a non-zoom or prime, you would need five to seven or more lenses to get the same focal range.
10.3 Wide-angle zoom lenses, like the Canon EF 16-35mm f/2.8L USM, provide a wide view of the scene.
Besides being convenient, zoom lenses are able to maintain focus during zooming. Thus, you can work on composition even after establishing focus at another focal length. To keep the lens size compact and to compensate for aberrations with fewer lens elements, most zoom lenses use a multigroup zoom with three or more movable lens groups.
Most mid-priced and more expensive zoom lenses offer high-quality optics that produce sharp images with excellent contrast. As with many Canon lenses, full-time manual focusing is available by switching the button on the side of the lens to Manual focus ( ). Getting a fast zoom lens means paying a higher price. Also, while zoom lenses allow you to carry around fewer lenses, they tend to be heavier than single focal-length lenses.
Some zoom lenses have a variable aperture. For example, the EF-S 18-135 f/3.5-5.6 IS STM is a variable-aperture lens. That means that at the widest focal length, the maximum aperture is f/3.5, and at the longer end of the focal range, the maximum aperture is f/5.6. In practical terms, this limits the versatility of the lens at the longest focal length for shooting in all but bright light or at a high ISO setting. And unless you use a tripod or your subject is stone still, your ability to get a crisp picture in lower light at f/5.6 will be questionable.
More expensive zoom lenses offer a fixed and fast maximum aperture. With a zoom lens that has an f/2.8 maximum aperture, you get faster shutter speeds that enhance your ability to get sharp images when handholding the camera. However, the faster the lens, the higher the price.
Primes
While you hear much less about prime, or single-focal-length, lenses than you hear about zoom lenses, prime lenses are worth careful consideration. With a prime lens, the focal length is fixed. This means you must physically move closer to (or farther from) your subject, or change lenses to change image composition. Canon has a nice selection of prime lenses, including the venerable EF 50mm f/1.4 USM and EF 100mm f/2.8L Macro IS USM.
10.4 A single focal-length lens is ideal for macro shots like this. Exposure: ISO 200, f/10, 1 second.
Unlike zoom lenses, prime lenses tend to be fast, with maximum apertures of f/2.8 or faster. Wide apertures allow fast shutter speeds that enable you to handhold the camera in lower light and still get a sharp image. Compared to zoom lenses, single focal-length lenses are lighter and smaller. In addition, single focal-length lenses tend to be sharper than some zoom lenses.
Working with Different Types of Lenses
Within the categories of zooms and primes, lenses are grouped by their angle of view. The angle of view is the area of the scene that can be reproduced by the lens as a sharp image. The image sensor is rectangular, but the image captured by the lens is circular, and it’s called the image circle. The image that’s captured is taken from the center of the image circle.
For a 15mm fisheye lens, the angle of view is 180 degrees on a full-frame 35mm camera. For a 50mm lens, it’s 46 degrees; and for a 200mm lens, the angle of view is 12 degrees. Simply stated, the shorter the focal length, the wider the scene coverage, and the longer the focal length, the narrower the coverage. The EF 8-15mm f/4L Fisheye USM lens was the world’s first fisheye zoom lens. At the 8mm setting, the lens delivers a 180-degree angle of view for full-frame cameras that results in a circular image.
The lens’s aperture range also affects the depth of field. The depth of field is affected by several factors including the lens’s focal length, aperture (f-stop), focus position, camera-to-subject distance, and subject-to-background distance.
Finally, the lens you choose affects the perspective of images. Perspective is the visual effect that determines how close or far away the background appears to be from the main subject. The shorter (wider) the lens, the more distant the background elements appear to be. The longer (more telephoto) the lens, the closer the elements appear.
Wide-angle lenses
Wide-angle lenses are aptly named because they offer a wide view of a scene. The wide-angle lens category provides angles of view ranging from 114 to 63 degrees. Generally, lenses shorter than 50mm are considered wide angle on full-frame 35mm image sensors. Excluding the 8mm and 15mm fisheye lenses, wide-angle lenses range from 17mm to 40mm on a full-frame camera. With the focal-length multiplication factor, you need lenses from 10mm to 22mm to get truly wide-angle shots.
Wide-angle lenses are ideal for capturing scenes ranging from sweeping landscapes to large groups of people, and for taking pictures in places where space is cramped. For Figure 10.5, I used the EF 24-70mm f/2.8L USM lens set to 24mm. The 24mm focal length gave an expansive view of the sunset, and heightened the dark clouds as they moved toward the horizon. Because I didn’t have a tripod with me, I shot wide open to get a fast enough handholding shutter speed.
10.5 A moderately wide 24mm lens gives an expansive view of the scene. Exposure: ISO 200, f/2.8, 1/50 second.
When you shoot with a wide-angle lens, keep these lens characteristics in mind:
• Extensive depth of field. Particularly at small apertures from f/11 to f/32, the entire scene, front to back, will be in acceptably sharp focus. This characteristic gives you slightly more latitude for less-than-perfectly focused pictures.
• Distortion. Wide-angle lenses distort lines and objects in a scene, especially if you tilt the camera up or down when shooting. For example, if you tilt the camera up to photograph a group of skyscrapers, the lines of the buildings tend to converge toward the center of the frame, and the buildings appear to fall backward (also called keystoning).
• Perspective. Wide-angle lenses make background objects appear far away from the subject, but these lenses also cause objects close to the camera to appear disproportionately large. You can use this characteristic to move the closest object farther forward in the image, or you can move back from the closest object to reduce the effect. Wide-angle lenses are popular for portraits, but if you use a wide-angle lens for close-up portraiture, keep in mind that the lens exaggerates the size of facial features closest to the lens, which is unflattering.
Telephoto lenses
Telephoto lenses offer a narrow angle of view, enabling close-ups of distant scenes. On full 35mm-frame cameras, lenses with focal lengths longer than 50mm are considered telephoto lenses, and the focal lengths range from 70mm to 800mm. On the 70D, with the APS-C-size sensor, 50mm lenses (equivalent to 80mm on the 70D) and longer provide a telephoto focal length.
Telephoto lenses offer an inherently shallow depth of field that is heightened when you shoot at wide apertures. On the 70D, 50mm, 85mm, and 100mm lenses are ideal for portraits, while longer, 200mm to 800mm lenses allow you to photograph distant birds, wildlife, and athletes. When you’re photographing wildlife, these lenses also allow you to keep a safe distance.
When you shoot with a telephoto lens, keep these lens characteristics in mind:
• Shallow depth of field. Telephoto lenses magnify subjects and provide a limited range of sharp focus. At wide apertures, you can reduce the background to a soft blur. Because of the extremely shallow depth of field, it’s important to get tack-sharp focus. Many Canon lenses include full-time manual focusing that you can use to fine-tune the camera’s autofocus.
• Narrow coverage of a scene. Because the angle of view is narrow with a telephoto lens, much less of the scene is included in the image. You can use this characteristic to exclude distracting scene elements from the image.
• Slow speed. Midpriced and even some expensive telephoto lenses tend to be slow; the widest aperture is often f/4.5 or f/5.6, which limits your ability to get sharp images without a tripod in all but the brightest light unless they also feature Image Stabilization. Due to the magnification, even the slightest movement is exaggerated. Regardless of the lens speed, using a tripod with telephoto lenses is always the best practice.
• Perspective. Telephoto lenses tend to compress perspective, making background objects in the scene appear close to the subject.
10.6 For this image, I used the EF 100-400mm f/4.5-5.6L IS USM lens, set to 250mm (equivalent to 400mm). Exposure: ISO 200, f/8.0, 1.3 seconds.
Normal lenses
Normal lenses offer an angle of view and perspective comparable to how your eyes see the scene. On full 35mm-frame cameras, 50mm to 60mm lenses are considered normal lenses. On the 70D, taking into consideration the focal-length multiplier, 50mm translates to 80mm. To get a 50mm view on the 70D, you must use a 31mm to 32mm lens zoom setting. The 50mm lens used to be the kit lens that came on new film cameras, and it was also the lens of choice for many photography greats, including Henri Cartier-Bresson. The 50mm was the first lens I used, and it is still one of my favorites due to its documentary look and feel, and fast aperture.
10.7 The EF 50mm f/1.4 USM lens is one of the oldest in Canon’s lineup, but it offers excellent contrast, as shown in this pet portrait. Exposure: ISO 400, f/2.8, 1/90 second.
When you shoot with a normal lens, keep these lens characteristics in mind:
• Natural angle of view. On the 70D, a 50mm lens closely replicates the sense of distance and perspective of the human eye. This means the final image will look much as you remember seeing it when you made the picture.
• Little distortion. Given the natural angle of view, the 50mm lens retains a normal sense of distance, especially when you balance the subject distance, perspective, and aperture.
Macro lenses
Macro lenses are designed to provide higher magnification by enabling you to move in very close to the subject. Depending on the lens, the magnification ranges from half life-size (0.5X) to 5X magnification. Thus, objects as small as a penny or a postage stamp can fill the frame, while nature macro shots can reveal breathtaking details that are commonly overlooked. Using extension tubes can further reduce the closest focusing distance. Macro lenses do double duty — in addition to macro shooting, they can also be used for standard types of photography, such as portraits.
If you’re buying a macro lens, you can choose lenses by focal length or by magnification. For example, if you’re shooting insects or other living creatures, a telephoto macro lens such as the EF 135 f/3.5L Macro USM enables you to maintain a distance from the subject and avoid disturbing the subject. However, due to the very shallow depth of field, it can be hard to render the entire subject in sharp focus. Thus, a standard macro lens such as the EF 100mm f/2.8L Macro IS USM may be a better choice.
10.8 The EF 100mm f/2.8L Macro USM lens allows focusing so close, I could almost fill the frame with this tiny, succulent blossom. Exposure: ISO 400, f/4.0, 1/50 second.
Choosing a macro lens by magnification means choosing how much larger the subject appears in the image than in real life. The EF 50mm f/2.5 Compact Macro has a magnification of 0.5X. The EF 100mm f/2.8L Macro IS USM has a life-size magnification, and the MP-E 65mm f/2.8 1-5X Macro Photo has a 5X magnification.
It is important to keep in mind that at 1:1 magnification and at maximum aperture, the depth of field with the EF 180mm Macro lens is less than 1mm. To maximize the depth of field, use a narrow aperture and keep the camera parallel to the camera’s focal plane.
With the shallow depth of field common in macro photography, be sure that the focus is tack sharp. You can tweak the camera’s focus by using full-time manual focus on some macro lenses such as the EF 100mm f/2.8L Macro IS USM. Also, the higher the magnification, the higher the risk of camera shake causing blur, so be sure to use a tripod and a Self-timer drive mode ( 
) or a remote release to fire the shutter.
Tilt-and-shift lenses
Tilt-and-shift lenses, referred to as TS-E lenses, alter the angle of the plane of focus between the lens and sensor plane to provide a broad depth of field even at wide apertures, and to correct or alter perspective at almost any angle. This enables you to correct perspective distortion and control focusing range.
Using tilt movements, you can bring an entire scene into focus, even at maximum apertures. By tilting the lens barrel, you can adjust the lens so that the plane of focus is uniform on the focal plane, thus changing the normally perpendicular relationship between the lens’s optical axis and the camera’s focal plane. Alternatively, reversing the tilt has the opposite effect of greatly reducing the range of focusing.
Shift movements avoid the trapezoidal effect that results from using wide-angle lenses pointed up (to take a picture of a building, for example). Keeping the camera so that the focal plane is parallel to the surface of a wall and then shifting to raise the lens results in an image where the perpendicular lines of the structure are rendered perpendicular and the structure is rendered as a rectangle.
Image courtesy of Canon
10.9 The TS-E 24mm f/3.5L II is one of the new tilt-and-shift lenses. It minimizes chromatic aberrations, provides an 80-degree view on a full-frame camera, and has a specially coated, aspherical element that reduces glare.
TS-E lenses have a range of plus/minus 90 degrees, making horizontal shift possible, which is useful when you are shooting a series of panoramic images. You can also use shifting to prevent reflections of the camera or yourself from appearing in images that include reflective surfaces, such as windows, car surfaces, and other similar surfaces.
All of Canon’s TS-E lenses are manual focus only. These lenses, depending on the focal length, are excellent for architectural, interior, merchandise, nature, and food photography.
Image Stabilized (IS) lenses
For anyone who has thrown away images blurred from handholding the camera at slow shutter speeds, the idea of Image Stabilization is a welcome one. Image Stabilization (IS) counteracts some or all of the motion blur from handholding the camera and lens, enabling you to shoot at slower shutter speeds than are generally considered acceptable. An IS lens shifts the optical system perpendicular to the optical axis to stabilize incoming light rays.
If you’ve shopped for lenses lately, you know that Image Stabilization comes at a premium price. IS lenses are pricey because they give you from 1 to 4 (or more) f-stops of additional stability over non-Image Stabilized lenses.
With an IS lens, miniature sensors and a high-speed microcomputer built in to the lens analyze vibrations and apply correction via a stabilizing lens group that shifts the image parallel to the focal plane to cancel camera shake. The lens detects camera motion via two gyro sensors — one for yaw and one for pitch. The sensors detect the angle and speed of shake. Then, the lens shifts the IS lens group to suit the degree of shake to steady the light rays reaching the focal plane. I handheld the camera and relied on Image Stabilization to get the image shown in Figure 10.10. I then converted the image to sepia using Nik Silver Efex Pro.
10.10 Image Stabilization allowed me to capture this image handholding the camera. Exposure: ISO 400, f/2.8, 1/25 second.
Stabilization is particularly important with long lenses, where the effect of shake increases as the focal length increases. As a result, the correction needed to cancel camera shake increases proportionately.
To see how the increased stability pays off, consider the rule of thumb for handholding the camera with a non-IS lens. The handholding rule says that the slowest shutter speed at which you can handhold the camera and avoid camera-shake blur is the reciprocal of the focal length, expressed as 1/[focal length]. For example, the slowest shutter speed at which you can handhold a 200mm lens and not get blur from hand shake is 1/200 second. If the handholding limit is pushed, then shake from handholding results in a blurry image.
Thus, if you’re shooting in low light, the chances of getting sharp images at 200mm are low because the light is too low to allow a 1/200 second shutter speed, even at the maximum aperture of the lens. You can, of course, increase the ISO sensitivity setting and risk introducing digital noise into the images. However, if you’re using an IS lens, the extra stops can mean that you don’t have to increase the ISO as much as you would with a non-IS lens.
If you want to pan or move the camera with the motion of a subject, then Image Stabilization detects panning as camera shake and interferes with framing the subject. To correct this, Canon offers two modes on IS lenses. Mode 1 is designed for stationary subjects. Mode 2 shuts off Image Stabilization in the direction of movement when the lens detects large movements for a preset amount of time. So, when you pan horizontally, horizontal Image Stabilization stops but vertical Image Stabilization continues to correct any vertical shake during the panning movement.
While super-telephoto lenses may be out of your price range, it’s a good idea to remain current with lens technology because it usually filters down to other, more affordable lenses. One such technology with super-telephoto lenses is a third Image Stabilization mode. This mode is designed for shooting action, where you need to quickly move the camera from one subject to another. With previous lenses, the view in the viewfinder sometimes did not keep up as the camera moved because the Image Stabilizer perceived the motion as camera shake.
To resolve this, Canon added Mode 3, in which the Image Stabilization motor begins working only when you make the picture. When you press the shutter button halfway, the lens calculates the amount of Image Stabilization needed, but the correction isn’t applied until you fully press the shutter button. Thus, you have a clear view of the subject to compose the image, and stabilization is applied at the moment the image is made. Mode 3 detects panning motion and only applies Image Stabilization at right angles to the direction of movement.
At this writing, the EF 300mm f/2.8L IS II USM, EF 400mm f/2.8L IS II USM, EF 500mm f/4L IS II USM, and EF 60mm f/4L IS II USM lenses all feature Mode 3 Image Stabilization.
Hybrid Image Stabilization for macro shooting
The EF 100mm f/2.8L II Macro USM lens features another iteration of Image Stabilization, dubbed Hybrid Image Stabilization (IS). This technology improves on standard Image Stabilization to compensate for both angle and shift camera shake that can occur in macro shooting. Angle shake is rotation around a point, as if the lens is roughly rotating in a circle, and normal Image Stabilization can correct it. While the camera may also shift in a plane parallel to the subject, this type of shift shake is hidden by the focal distance in nonmacro shooting.
However, in macro photography, for which the focusing distance is shorter and the magnification is higher, shift shake is more visible. The classic rule of thumb says you need a shutter speed that is equal to or faster than the reciprocal of the lens focal length. Therefore, if you’re shooting at a 180mm focal length, the minimum shutter speed for handholding the camera would be 1 over 180, or 1/180 second. However, for macro shooting, the stabilization needed is 1 to 2 stops greater than what’s needed for nonmacro shooting.
To compensate, Hybrid IS uses the traditional vibration gyro to detect angular motion and adds an acceleration sensor to detect parallel shift shake. Thus, the camera can detect and compensate for camera movement in three directions. With the 100mm macro lens, this means that you can use shutter speeds roughly 3 stops slower at 0.5X magnification, and approximately 2 stops slower at 1X.
You can calibrate lenses that you use on the 70D. Aligning the focus of lenses is detailed in Chapter 6, and setting peripheral illumination and chromatic aberration correction is detailed in Chapter 2.
Lens Accessories
Lens accessories can be as simple as a lens hood to avoid flare, a tripod mount to change between vertical and horizontal positions quickly without changing the optical axis or the geometrical center of the lens, or a drop-in or adapter-type gelatin filter holder. Other options include using extension tubes, extenders, and close-up lenses that increase the focal range, but decrease the focusing distance to provide flexibility for the lenses you already own. These accessories are not only fairly economical, but they extend the range and creative options of existing and new lenses.
Extenders
For relatively little cost, you can increase the focal length of any lens by using an extender. An extender is a lens set in a small ring mounted between the camera body and a regular lens. Canon offers two extenders, the EF 1.4X III and EF 2X III, that are compatible only with L-series lenses. Extenders can also be combined for even greater magnification.
For example, using the Canon EF 2X III extender with a 600mm lens doubles the lens’s focal length to 1200mm before applying 1.6X. Using the Canon EF 1.4X III extender increases a 600mm lens to 840mm.
Image courtesy of Canon
10.11 The Extender EF 1.4X III and EF 2X III are excellent accessories that increase a lens’s focal range by 1.4X or 2X, respectively.
A disadvantage to using extenders is that they reduce the light reaching the sensor. The EF 1.4X III extender decreases the light by 1 f-stop, and the EF 2X III decreases it by 2. However, an obvious advantage is that, in addition to being fairly lightweight, extenders can reduce the number of telephoto lenses you carry.
The latest EF extenders offer a new optical design that produces sharper images with less chromatic aberration along high-contrast edges. The fluorine coating is designed to repel oil and water, and make cleaning the lens easier.
Further, the new EF extenders have integrated processors that gather and transfer information from the lens to the camera, including the focal length, focus distance, and Image Stabilization. Also, if you set AF Microadjustment, you can include the extender with the lens during the process of adjusting the lens.
If you’re using an extender, be sure to first attach the lens to the extender, and then attach both to the camera so that the camera can detect both the extender and the lens attached to it. If you first attach the extender without the lens to the camera, the camera will recognize the extender but not the lens you attach to it.
Extension tubes and close-up lenses
Extension tubes are close-up accessories that provide magnification increases from approximately 0.3 to 0.7, and they can be used on many EF lenses, though there are exceptions. Extension tubes are placed between the camera body and lens and connect to the camera via eight electronic contact points. Extension tubes can be combined for greater magnification.
Canon offers two extension tubes, the EF12 II and the EF25 II. Magnification differs by lens, but with the EF12 II and standard zoom lenses, it is approximately 0.3 to 0.5. With the EF25 II, magnification is 0.7. When combining tubes, you may need to focus manually. Extension tubes are compatible with specific lenses. Be sure to check the Canon website for lenses that are compatible with extension tubes.
Additionally, you can use screw-in close-up lenses. Canon offers two lens series that provide enhanced close-up photography — the 500D and 250D series that you can buy by filter size.
10.12 The 100mm f/2.8L Macro IS USM lens combined with a 20mm Kenko extension tube enabled a very close shooting distance so I could isolate focus on a thin line in this daisy petal. Exposure: ISO 800, f/4.0, 1/100 second, -2/3 exposure compensation.