Balancing Your Colors

To eliminate any color casts that are in your image, you'll need to look for color contamination in the gray areas of your image, and then use that information to help correct the whole image. Three standard areas of your image will usually contain a shade of gray: the brightest area of the image, which is known as the highlight; the darkest area of the image, which is known as the shadow (on most photos, the highlight and shadow areas shouldn't contain color); and a gray object in the image.

Now that we know which areas need to be adjusted, let's go ahead and make the actual adjustment. Start by choosing Image > Adjustments > Curves. We'll be working with all three eyedroppers that show up in the lower right. All three adjust the area you click on so that it ends up with a balanced combination of red, green, and blue, which effectively removes any color contamination for that area. The only difference between the eyedroppers is that the one full of black makes things really, really dark, the eyedropper full of white makes things really bright, and the middle eyedropper doesn't change the brightness of an area. We'll use those to adjust the shadow, highlight, and gray areas, respectively. But we first have to set up things correctly.

Double-click on the right most eyedropper to bring up the Color Picker. This eyedropper will be used to adjust the brightest part of the image (the highlight). You don't want the highlight to become pure white because it would look too bright. You want to reserve pure white for those areas that shine light directly into the camera lens (like lightbulbs and shiny reflections). That means you want the highlight to be just a tad bit darker than white.

If you remember the chapter on grayscale images (Chapter 5, “Optimizing Grayscale Images”), I mentioned that the lightest percentage of ink you can use on a printing press is usually 3% (5% for some newspapers). That means we don't want to use less than 3% of any ink in the brightest part of our image; otherwise, we might lose critical detail. But we're adjusting our image in RGB mode, and when you do that, you'll be using a numbering system that ranges from 0 to 255, not 0% to 100%. So let's figure out how to create a minimum of 3% ink in RGB mode.

After double-clicking the rightmost eyedropper, set the saturation setting (S) to 0 and the brightness setting (B) to 100%, and click on the number next to the letter B (brightness). Use the down arrow key to change that setting until the magenta (M) and yellow (Y) readouts indicate at least 3%. Cyan (C) will be higher, but don't worry about that. At this point, the numbers will show you exactly what RGB values are needed to produce that much ink—in my case, 240R, 240G, 240B (Figure 8.7).

Now, on to the dark side. We're going to make the darkest area of your image pure black (0R, 0G, 0B) in order to use the full range your computer monitor is capable of displaying. Black wouldn't be a good choice if you are really outputting to a printing press (you'd lose a lot of detail), but we'll set it up so that Photoshop will adjust your image automatically if you have to convert to CMYK mode.

That way we'll be guaranteed that no detail will be lost no matter what the output. So, double-click on the leftmost eyedropper and make sure it's set to black. When you click OK in the Curves dialog box, Photoshop will ask you if you would like to “Save the new target colors as the defaults?”. I suggest that you click the Yes button so that Photoshop remembers those settings and uses them every time you use the eyedroppers to color correct your images.

Now that we have everything set up properly, let's start adjusting images. Open any image that needs to be color corrected, and then choose Layer > New Adjustment Layer > Curves. Click the black eyedropper and then click on the shadow area. When I mention the shadow, I don't mean a traditional shadow like the kind cast from an object; instead, I'm talking about the darkest area of an image. All images have a shadow area, but it can sometimes be hard to locate because there may be multiple candidates. (I'll show you how to find them before we're done with this chapter.)

Once you've done that, click on the white eyedropper and then click on the brightest part of the image. That is the brightest area that should still contain detail. You'll often find it in a white shirt collar or button, a Styrofoam cup, the whites of someone's eyes, or a sheet of paper. In Figure 8.8, the brightest white falls on a fold in the sheer curtain material.

Finally, click on the middle eyedropper and then click on any area that should be gray in the final image—not bluish gray or pinkish gray, but pure gray (also known as neutral gray). You might have to really hunt for a gray; it is not always obvious. It could be a sweatshirt, a white shirt, or the edge of a book. On the other hand, you might run across an image that has dozens of gray areas to choose from. In that case, try to pick one that is not overly bright or dark, because we are already adjusting the highlight and shadow of the image. The closer we get to a middle gray, the more effective your adjustment will be. If you have any doubt at all that the area you have chosen should be gray, just experiment by clicking on one area to see what happens; then press Command-Z (Mac) or Ctrl-Z (Windows) to undo the change, and then try another area. Repeat this process until you've found an area that really causes the image to improve, but don't try too hard—not every image contains a true gray. For example, you might not be able to find one in a photograph of a forest. If you can't find one, then (of course) don't adjust it.

Using Threshold to Locate Highlight and Shadow

If you hate having to guess at anything, here's how to find the highlight and shadow areas without guessing. Choose Image > Adjustments > Threshold and move the slider all the way to the right; then slowly move it toward the middle (Figure 8.9). The brightest area of the image will be the first area that shows up as white (you can use the up and down arrow keys to move the slider). You don't want to find the very brightest speck (that could be a scratch or a reflection on something shiny), so be sure to look for a general area at least five or six pixels in size (something that's easy enough to click on without having to be overly precise). Once you've found the correct area, you can hold down the Shift key and click on that part of your image to add a color sample to that area (Figure 8.10). (You have to hold Shift only if you're still in an adjustment dialog box like Threshold.) A color sampler is simply a visual reminder of where that area is.

Now let's use Threshold to find the darkest area of the image. This time, start with the slider all the way to the left, and then slowly move it toward the center. This will show you where the darkest area of the image is hiding. You don't want to find the darkest speck (that could be dust), so be sure to look for a general area at least five or six pixels in size. Once you've located the shadow, Shift-click on that area to place a sample point on top of it, and then click Cancel to get out of the Threshold dialog box. If you click OK instead of Cancel, your image will remain completely black and white. Now you should have two crosshairs on your image, one for the highlight and one for the shadow, as shown in Figure 8.11. When you use the eyedroppers in the Curves dialog box, you can press Caps Lock to turn your cursor into a crosshair, which will make it easy to tell when you're lined up with those color samplers. You can get rid of the color samplers by choosing the Color Sampler tool (it's hidden under the Eyedropper tool) and clicking the Clear button in the Options bar.

Only use those eyedroppers that help to improve the look of your image. If one of them shifts the colors in an undesirable way, press Command-Z (Mac) or Ctrl-Z (Windows) to undo that step and either try another area or don't use that eyedropper. Just because a single eyedropper harms your image doesn't mean that the other two eyedroppers won't help it, so always try all three even if you think they might not help the image. You'll be surprised at how often all three can be used. You'll find that the white eyedropper doesn't help images that have desirable color casts. That's where you want the image to look warm or cool. Examples would be dinner by candlelight, a fireplace, and sunrise or sunset. And if you find that none of the eyedroppers seems to help, be sure to check out the techniques I mention in the “Color Manipulation” chapter.

Now let's explore two alternative methods for adjusting the highlight, shadow, and gray areas of an image.

Using a Grayscale to Correct Multiple Images

Here's an interesting trick I like to use when I know I'll be color correcting a large number of images that will be shot under the same lighting conditions, or when I photograph artwork. If you stop by a high-end camera store, you can ask for a grayscale (also known as a step wedge or a grayscale step wedge—Figure 8.12). Once you have one, you can place it in the scene where you are about to take a large number of photos (let's say for a yearbook or a product brochure) or when shooting any kind of art. Now, this is important—before you start shooting your actual scenes, you will want to take a photograph of the wedge under the exact same lighting conditions and exact same film type that you'll be using for the rest of the photos. That way you can use it as a reference that will pick up the color influence of the lighting and film.

Once the images are developed, scanned, and loaded into Photoshop, create a new Curves Adjustment Layer. Click on the white eyedropper and then click on the brightest gray rectangle on the grayscale. Next, click on the black eyedropper and then click on the darkest rectangle; and finally, click on the middle eyedropper and then click on the middle gray rectangle. That should remove any color cast that was present in the image.

You can apply that same adjustment to the other images by dragging the Curves Adjustment Layer from the grayscale image and dropping it onto another image that was photographed under the same lighting conditions. That way you can perform color correction with no guesswork and quickly apply the same adjustment to a large number of images.

You might find that this technique changes the contrast of your image too much. If that's the case, then either just use the middle eyedropper (skipping the other two) or use a Blending mode to control how the adjustment affects your image. If you applied your image directly (by choosing Image > Adjustments > Curves), then choose Edit > Fade Curves right after applying the adjustment and change the pop-up menu to Color. Or, if you used an Adjustment Layer, change the Blending mode menu that's found at the top of the Layers palette to Color. That will prevent the adjustment from changing the brightness or contrast of your image, but will still allow it to shift the colors.

Auto Color

Photoshop includes a great feature that attempts to automate the process of color correction: Auto Color (Figure 8.13). It uses the same general concepts we've been talking about in this chapter, and you'll find that it works well with a large variety of images. You can access Auto Color by creating a new Curves Adjustment Layer and then clicking on the Options button. The Shadows, Midtones, and Highlights settings use the same setting that we specified when we double-clicked on the eyedroppers in the Curves dialog box. The only difference is that Photoshop attempts to locate the highlight, shadow, and gray areas automatically. This dialog box is interactive—changes will immediately affect the image. I'd set the Shadows Clip value to 0.25% and the Highlights Clip value to 0.10%, and then choose the Find Dark & Light Colors option at the top of the dialog box so that Photoshop uses Threshold to find the bright/dark areas and applies the eyedroppers to them. Then turn on the Snap Neutral Midtones check box so it uses the middle eyedropper on areas that are close to being gray. I find that this automated feature works on a surprising number of images. But as with most automated features, you'll find that you have to take over and use the old eyedroppers technique whenever Auto Color fails to deliver a satisfactory result.

If you find that the highlights in your image become blown out (no detail), you can click on the White Clip setting and press the down arrow key on your keyboard a few times until you see the detail return. You can do the same thing with the Black Clip setting to make sure you don't lose detail in the shadows of your image. I generally use the .10% setting that I mentioned earlier, and I only change it when I actually notice that I'm losing detail. If you're usually satisfied with the .10% values, then be sure to turn on the Save As Defaults check box so Photoshop will remember those settings. Then, you can quickly apply the new default settings to any image by choosing Image > Adjustments > Auto Color. And if you notice the contrast of the image changing too much, choose Edit > Fade Auto Color right after applying that command and set the pop-up menu to Color. That will prevent any brightness or contrast shifts.

Adjusting the highlight, shadow, and gray areas of an image can dramatically improve the quality of an image. But even with those adjustments, you occasionally need to fine-tune any skin tones that might be in the image.