Using Auto Exposure

Located directly beneath the histogram is a small Auto Exposure button that can automatically set the Exposure slider. This button works only when you're adjusting a raw image.

Auto Exposure analyzes your image and calculates an exposure setting that will distribute the tones more evenly across the histogram (Figure 6.11). Auto Exposure is smart enough to know that if your original image is very bright or very dark, then it should not simply shove all the tones into the middle of the histogram. Instead, it will perform an adjustment that's enough to stop egregious clipping, but without going too far.

Figure 6.11. The Auto Exposure button, located directly beneath the histogram, will try to calculate an exposure setting for a raw image. The image on the right has had Auto Exposure applied.

Applying Auto Exposure is often a good way to start your Exposure adjustment. Let Auto Exposure provide a ballpark exposure setting and then tweak the setting by hand afterward.