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The Design Center, DT&G / Photoshop Department / Fixing a Color Cast in Photoshop  

Ladies and Gentlemen, we welcome back Mr. Deke McClelland to once again share his Photoshop expertise in this issue of DTG!

Fixing a Color Cast with Photoshop

[Editor's Note: Here's another of those frequent questions we get in the Photoshop 911 emergency room. The Photoshop One-on-One, has just about all of the techniques you need to master Photoshop! Thanks to O'Reilly Publishing we're able to bring the technique to you in its entirety! ] Read our Editor's Choice Review of Deke's "Photoshop CS2 One-on-One"

Deke McClelland writes...

One of the most common color problems associated with digital images and photographs in general is color cast, a malady in which one color pervades an image to an unrealistic or undesirable degree. For example, an old photograph that has yellowed over the years has a yellow cast. A snapshot captured outdoors using the wrong light setting may suffer a blue cast.

Naturally, Photoshop supplies a solution, and a simple one at that. Color Cast

Designed to remove a prevailing color cast and restore the natural hue and saturation balance to an image, Image > Adjustments > Variations may be Photoshop's most straightforward color adjustment command.

Rather than previewing your corrections in the main image window, as other commands do, Variations presents you with a collection of thumbnail previews. Your job is to click the thumbnail that looks better than the one labeled Current Pick. You can click as many thumbnails as you like and in any order.

The following exercise walks you through a typical use for the Variations command:

1. The image. Captured using a decidedly incorrect light setting during an intense gingerbread house construction project--one of the few activities that lets you marry the crafts of Julia Child and Frank Lloyd Wright--this image suffers from what I like to call "An Unbearable Preponderance of Orange" (see Figure 3-6).

      The problems with the image in Figure 3-6 bear some resemblance to those that we corrected with the Levels command in Lesson 2 (see "Adjusting Brightness Levels" on page 42). And in truth, you can fi x much of what ails this photograph with Levels. But because the main offender here is color cast, Variations is the easier solution. Unlike Levels or any of the other commands from Lesson 2, Variations can recruit information from one channel and bring it into another, an enormous advantage when correcting color balance.

Variations 2. Choose the Variations command.
Choose Image > Adjustments > Variations, as shown in Figure 3-7, to display the gargantuan Variations dialog box.

By default, Photoshop does not include a shortcut for Variations. Under Windows, you can access the command by pressing Alt and typing "Ian." On the Mac, you have to assign a custom shortcut with Edit > Keyboard Shortcuts or use mine. If you loaded Deke Keys (see the Preface, Step 10, page xix in the book), you'll see that I've reassigned the shortcut that was formerly assigned to Color Balance, Ctrl+B .

3. Click the Original thumbnail.
Variations is one of the few color adjustment commands that automatically remembers the last adjustment you applied. This is helpful when revisiting the dialog box if a correction doesn't quite turn out the way you had hoped. But for this exercise, you'll want to clear the old correction (if indeed there was one) and start from scratch. Clicking the top-left thumbnail, the one labeled Original, does exactly that (see Figure 3-8).

Select Original and Midtones 4. Select the Midtones option.
Like Levels, the Variations command lets you apply your changes to the highlights, midtones, or shadows in an image. You do so by selecting one of the first three radio buttons near the top of the dialog box. When correcting a color cast, however, you almost always want the default setting, Midtones. (Shadows is sometimes useful; Highlights almost never.) Make sure Midtones is selected.

5. Turn off Show Clipping.
When and if you adjust highlights, shadows, and --as we'll see-- saturation values, some colors may exceed the brightness range in one of more color channels. These colors are clipped to white or black. When the Show Clipping check box is on, as by default, Photoshop tries to warn you about these clipped colors by inverting them. The problem is, the warning is misleading (just because a color is clipped in one channel doesn't mean it is in another) and blocks what is already a small view of your image. For my part, I always turn Show Clipping off.

6. Set the Fine/Coarse slider to the middle.
Midtones settingsThe slider bar, which is labeled Fine on one side and Coarse on the other, lets you modify the intensity of your edits. Under Windows, set the triangle to the exact middle of the slider. Strangely, on the Mac, there is no exact middle. The equivalent setting is three tick marks over from Fine, as shown at right.

7. Click the More Cyan thumbnail twice.
When Shadows, Midtones, or Highlights is active, the central portion of the dialog box contains a total of seven thumbnails: six color variations grouped around Current Pick. Click any color variation thumbnail to nudge the image toward a range of hues.

So, for example, More Yellow represents not simply yellow, but a whole range of colors -- amber, chartreuse, and so on -- that have yellow at their center (as you'll learn about in "The Visible-Color Spectrum Wheel" on this page).

The Variations Palette

      Thumbnails arranged across from each other --so that they form a straight line with respect to the central Current Pick thumbnail-- represent complementary colors. This means they form neutral gray when mixed together. For example, More Yellow appears on the other side of the Current Pick thumbnail from More Blue, so yellow and blue are complementary. In the Variations dialog box, Photoshop treats complementary colors as opposites. In other words, if you click the More Yellow thumbnail, Photoshop adds yellow and subtracts blue.

Our problem color is red, and based on the position of the More Red thumbnail, red's complement must be cyan. We have a decent amount of red to get rid of, so click More Cyan twice. (Be sure to get both clicks in; if you click too fast, Photoshop has a tendency to ignore one.) All the thumbnails, except the one la- beled Original, update to refl ect the change, as in Figure 3-10.

NOTICE In the next step we'll work with the intensity and texture of the image...


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