Color Correction Tips

The Extra-Strength Tips for the Clients and Friends of Ben Willmore (www.digitalmastery.com):

Since I've been asking you for images that need color correction, I thought it would be appropriate to get into some color correction tips. This tip will talk about the absolute basics of color correction and then we'll build on it in future tip letters. But, just because we're talking about the basics, don't think these techniques are trivial. I'd say that they could help about 90% of the images that have been submitted to me (to submit your own images, visit www.digitalmastery.com/submit )

The general concept behind color correction is that most photographs don't contain much of any color in the absolute brightest or darkest areas (you simply can't have much color in overly bright or dark areas). If a color has contaminated your image (from scanning, fading or any other source), then we can measure what color it is and figure out how big of a correction is needed by examining the brightest and darkest areas of the image (known as the highlight and shadow areas).

Photoshop doesn't know how to create perfect looking grass, or perfect skies, or skin tones, but it does know how to make a perfect shade of gray. So, after we analyze the highlight and shadow areas of an image, we'll check to see if there are any problems in areas that should be gray (non colored areas). Let's get to it and see how quickly we can improve our images.

If you're not used to finding the absolute brightest and darkest areas in your images, then try choosing Image>Adjustments>Threshold. Move the slider all the way to the right and then slowly move it towards the middle until you see a small blob of white appear (not just single pixels, but 5-6 of them clumped together). That's the brightest part of your image, so turn the Preview checkbox off and then back on again so you can see which part of your image that is. Then, to find the darkest part of your image, move that slider all the way to the left and then move it towards the middle until you see a small black blob. Now, turn preview off and back on again so you'll know where that spot is in your image. Once you know where those two spots are, click Cancel, otherwise your entire image will end up looking solid black and white. When you're finding the highlight and shadow areas be sure to ignore any white or black borders around your image, you want to find the highlight and shadow of the image itself.

Now, choose Image>Adjustments>Curves (you can use Levels as well) and take a look at the eyedroppers that show up in the lower right. Clicking on one of those eyedroppers and then clicking on your image will pull all the color out of an area, making it a neutral gray (meaning gray with no hint of a color in it). The only difference between the three eyedroppers is that the one full of white makes things as bright as they can get, while the one full of black makes things as dark as possible, and the middle one doesn't change the brightness of an area. But before we start using them on our images, we're going to have to set them up just right.

Double-click on the white eyedropper and set the RGB numbers to 240 each (even if working in CMYK mode). That will make sure we don't blow out the highlights of your image to pure white, instead, they'll end up around 3% gray. You usually want to reserve pure white for areas that are reflections on shiny objects. You're welcome to double-click on the black eyedropper and set it to 12, which should make you end up with 95% in the shadows, but that one's less essential and I sometimes like pure black shadow areas. You don't have to mess with the setting on the middle eyedropper since it doesn't change how bright things are. Once you've set those up, then click OK in the Curves dialog box so that from now on, Photoshop will use those settings as the defaults.

Now it's time to color correct our images. All you have to do is choose Image>Adjustments>Curves (or use an Adjustment Layer), click on the white eyedropper, click on the highlight area that you found when using threshold, click on the black eyedropper and then click on the shadow area. If either one of those doesn't improve your image, then type Command-Z (Mac), or Ctrl-Z (Win) to undo that step and only use the eyedroppers that help. The last step is to search through the image for an area that looks like it shouldn't have color in it (a gray area). Sometimes it's a gray sweatshirt, or the shadow area on a white shirt. Some images simply don't have a gray area and in those cases, you simply skip the middle eyedropper.

You'll find that the white eyedropper doesn't really help when you have an image that has what I call a desirable colorcast. Examples of that would be sunset, candlelight, a fireplace and other images where you want the warmth of the light source to influence the overall look of the image.

Ok... that's enough for now. You might have noticed that this tip was a bit more involved than usual. It's just one way I'm responding to the comments you guys gave in the survey I did a few weeks ago. I'd usually reserve this type of technique for my books, videos and other indepth products, but you guys have been asking for more indepth tips. There's much more indepth coverage of color correction in Chapter 9 of my Photoshop 7 Studio Techniques book, which you can buy at www.digitalmastery.com/book (hint, hint!!) And if you want to continue receiving more indepth tips, please help me out my submitting all your problem images so I can develop better techniques (details at www.digitalmastery.com/submit ).

-Ben