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 are able to 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.

For example, look at the two typical tourist snapshots presented side by side in Figure 4.1. The camera was mounted on a tripod for both, so the only way you can really see that they are two different images is by examining the differences in the way the water flows in the ice-free area of the foreground. However, the pair of pictures does vary in exposure. The version on the left was underexposed, which helps bring out detail in the snow and sky in the background, but makes the shadows of the building look murky and dark. The overexposed version on the right offers better exposure for the foreground area, but now the brightest areas of the building and sky are much too light.