Last month, I explained a method for finding and setting your image’s black and white points. Using that procedure adds just the right amount of contrast to a flat image, and sometimes corrects color issues, too. Yet finding the black and white points is often just the first step. In plenty of photographs, a color cast still remains.

For these, try the gray dropper. The concept is simple enough: Just click on a point that’s supposed to be neutral gray, and your whole image’s colors follow suit, automatically eliminating any visible color casts.

But what if you can’t find a gray tone in your image, or have several areas that look like they could be neutral gray?

Here’s a trick to help you find the best neutral point. As in last month’s Software Workshop, it uses a Threshold Adjustment Layer. And once again, it’s much easier to do in Adobe Photoshop CS4, though it will work with previous versions.

F.Y.I. This month’s software workshop begins with last month’s steps already applied. But if your image already has good contrast, or if you have a method for fixing contrast that you prefer, you can still use this tutorial to find a neutral and fix your color. Just add a threshold adjustment Layer between steps three and four.

Step 1: If you haven’t already, set the black and white points for your image according to the April 2010 Software Workshop: Create a Threshold Adjustment layer, slide it left to find and mark the black point, to the right to find and mark the white point, and then create a Levels Adjustment layer. Turn off the Threshold layer, then use the black dropper to click on your black target, and white to click on your white target. Full Explanation