Photo editing: correcting exposure

It's sometimes hard to tell whether a photo is properly exposed because you can't tell if the problem is the angle of your computer screen or the photo itself. But while your screen may lie to you, the histogram will not.

Check out this photo. There's lots of white, but is it properly exposed?

© Holly A. Heyser 

The histogram tells you the answer:

The bars in a histogram proceed from black on the left to white on the right. If there is white in a photo, you should see bars all the way to the right. We know snow should be white, so we know this photo is underexposed.

You can use the histogram on your camera screen to check exposure while you're in the field, but here I'll focus on correcting exposure in Photoshop. The best place to do that is in Camera RAW.

If you shoot in RAW - which you should always do - clicking on the file to open it will always open it in Camera RAW. If for some unfortunate reason you shot JPGs, viewing them in Bridge will allow you to open them with Camera RAW.

Here's how the image above looks in Camera RAW (click on it to look at the image at full size):

Look for the exposure slider on the right side. Click and drag it until that wall of white bumps up to the right side of the histogram:

Much better, right? Maybe. If that bar on the right is maxed out, you might have blown-out highlights. This is not necessarily a bad thing, but you should click on that triangle in the upper right-hand corner to reveal the blown-out highlights in red. In this case, it's nothing troubling:

If it had been troubling, though, I would have had two choices: One, reduce the exposure a bit, or two, use the recovery slider right underneath the exposure slider. Dragging that to the right recovers detail in the blown-out areas.

Here's the before-and-after:

© Holly A. Heyser