What a Histogram Shows

A histogram shows the distribution of tones, or the contrast, in an image. Brightness, from black (on the left) to white, appears on the horizontal axis. The vertical axis shows the number, or weight, of pixels at each brightness level. In an average scene, a well-exposed image shows tonal distribution and weight distributed fairly evenly across the entire histogram.

How to Identify Problem Pictures

When examining a photo's histogram on the LCD of your camera, you are looking to see if the pixels drop off sharply at either end of the histogram. A steep drop off is called clipping and it indicates that some of the pixels in the image are either overexposed (right side) or underexposed (left side). When pixels are clipped, they are either pushed to pure white or black and lose all detail.

What Is Shutter Lag?

The delay between the time you press the shutter release button and the time when the camera takes the picture is called shutter lag. Because of this delay, you can miss capturing the action, such as the moment a family member blows out candles on a birthday cake, or when a basketball player moves a ball down the court.

Avoid Missing Critical Moments

To work around shutter lag, you can anticipate the action. Focus on where the action will happen and press the shutter release button halfway down, wait for the action, and then take the picture. You should also turn off red eye reduction if you use a flash, and you should remove accessory lenses and avoid using extreme zoom settings. Also switch to burst mode to capture a rapid sequence of pictures with no shutter lag.

What Are Blowouts?

When you take pictures in a scene with very bright and very dark areas, the brightness differences may exceed the camera's dynamic range, or its ability to record both very bright and very dark areas. As a result, very bright areas often lack detail and appear as solid white.

How to Avoid Blowouts

It is particularly important to avoid blowouts in the main subject area. One of the most problematic subjects is a wedding dress on a bright, sunny day. To avoid blown highlights, switch to a semi-automatic or manual mode, and then select spot or center-weighted metering. The camera meter weighs exposure primarily for light falling on the subject rather than averaging the entire scene, ensuring accurate subject exposure, as shown here. If the dress is not properly metered, it will blow out and the details of the dress will be lost.

What Is Camera Shake?

Newer pocket- and palm-size digital cameras make everyday snaps inviting and easy. Because of their low weight, avoiding camera shake – blur from hand movement during shooting – can be challenging. Whenever you have the zoom lens extended to telephoto, it is more susceptible to shake.

How to Avoid Camera Shake

In all but very bright scenes, you need to steady the camera by leaning against a solid surface such as a wall, or by setting the camera on a solid surface when taking the picture. Alternatively, you can buy a tabletop tripod that ensures sharp images. A simple solution is to carry a small sandwich bag filled with dried beans. It is lightweight and form-fits the camera to a fence post or a pillar.

What Causes Undesirable Color Casts?

Modern digital cameras produce accurate color in photos automatically without using additional settings. Color casts occur when you take pictures in one type of light, such as shade, but the camera either cannot determine the color temperature of the light source or the camera is set to a type of light, such as bright sun. In the photos shown here, one was shot in automatic mode and the colors of the incandescent lights cast a warm, reddish orange. The second photo was taken with the white balance, or WB, setting deliberately set wrong to show what a difference it makes. To produce accurate colors, the camera must be set for the light in the scene. See Chapter 3 for more information about light.

Set White Balance to Get Accurate Color

When shooting outdoors, you can usually use the automatic settings with confidence. However, you may want to experiment with different white balance, or WB, settings, to become familiar with the effect that each setting produces and to help you avoid taking pictures with unnatural color casts. To set the white balance, use the camera's menu – usually the shooting menu – to select a setting that matches the scene light, such as daylight, fluorescent, or tungsten (common household light). Be careful when you use manual settings: It is easy to forget that by selecting a white balance setting, you have turned off the automatic white balance.

How Digital Zoom Works

With digital zoom, the camera takes the center of the image, crops the edges, and then expands the center section to full-image size. Some cameras interpolate, or add pixels into the image, to bring the image to full resolution size. Because interpolation guesses where to add pixels to the image, the results are never as good as using optical zoom.

How to Avoid Using Digital Zoom

On all digital cameras that have an optical zoom, you can turn off digital zoom by selecting an option on one of the camera's menus. Most cameras with digital zoom include an audible signal or LCD indicator, to tell you when to move from optical to digital zoom. Use the indicators to avoid activating the digital zoom feature.

Recognize Digital Noise

When you take digital pictures in low-light scenes, you often see brighter, colored pixels scattered throughout the dark and shadow areas of the image. Although you may not see noise on the LCD without zooming in, you see it on the computer at 100 percent or 200 percent magnification, and in prints larger than 4 by 6 inches.

How to Avoid Digital Noise

Both high ISO settings and long exposures contribute to digital noise. Increasing the ISO setting decreases exposure times, so it is best to find a balance between the two. To reduce digital noise in low-light shots, select a higher ISO setting, such as ISO 800, and use a tripod. Take some test shots and in the LCD display zoom in as close as possible to see if the noise is excessive. Adjust the ISO settings so the shutter time remains less than 2 seconds if possible. Some cameras offer noise reduction for shutter speeds less than 1/20 of a second; this feature does not completely eliminate the noise but it does reduce it.

Avoid High-Contrast Settings

More and more cameras offer options for adjusting image sharpness, contrast, and color saturation. Although these can be useful for snapshots, they also produce images that look artificially enhanced. If your camera offers a contrast level adjustment, you should not select the high-contrast option to avoid taking contrasted images.

Avoid Increased Saturation Settings

Options for increasing saturation, or intensity of colors, add vibrancy to the colors but they also produce images that look unnaturally vivid. If you want more vivid images, wait to increase saturation in an image editing program.

Fine-Tune Exposure Settings

After several weeks of taking pictures with your camera, you can tell if the camera consistently overexposes or underexposes images. You can select positive or negative exposure value (EV) settings to compensate for consistent exposure problems. For example, if your camera overexposes images (they are too light), choose a negative EV setting.

Fine-Tune White Balance and Flash Settings

Like exposure settings, you can adjust settings, such as white balance and flash intensity, on many digital cameras. For example, if you take pictures indoors under the same kind of household light, you can select a positive or negative tungsten white balance setting to get more accurate color. You can also adjust the flash to reduce the output for better flash picture results, as shown here.