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By Root 1749 0

edit the color in a flattened pixel image can be achieved using just Levels, Curves and Hue/Saturation. But before we get into how these should be used, we should take a quick look at the Variations adjustment (Figure 5.46). This image adjustment is a good learning tool for beginners, because all the basic image editing tools are combined in a single interface (you can also see how Variations adjustments relate to the color wheel diagram shown in Figure 5.45). Having said that, I would not advise using Variations as a general tool for color correction because it does nothing more than provide a Levels style Gamma slider control to adjust the individual color channels or overall brightness. Anything you do using Variations can be done more simply using Levels (or more accurately using Curves), plus the Variations adjustment can only be applied to 8-bit images. While Variations does have a Saturation control, the Hue/Saturation adjustment provides more versatile controls. The same goes for the Color Balance image adjustment. This too is simply offering you another way to apply Levels style adjustments.

Figure 5.46 The Variations interface lets you modify the color of the shadows, highlights or midtones separately. For example, clicking on the More Red thumbnail image will cause the red variant to shift to the center and readjust the surrounding thumbnail previews accordingly, and clicking on the More Cyan thumbnail restores the central preview to its original color balance. In this respect, Variations is just like the Color Balance adjustment, but you also have built-in saturation adjustments and a lighter or darker option. Variations may be a crude tool for color correction work, but it is nonetheless a useful means by which to learn color theory before you proceed to applying the principles learnt here to working with Levels or Curves.

Figure 5.45 The Variations dialog displays color balance variations based on the color wheel model. Here you see the additive primaries (red, green, and blue) and the subtractive primaries, (cyan, magenta, and yellow) placed in their complementary positions on the color wheel. Red is the opposite of cyan; green is the opposite of magenta; and blue is the opposite of yellow. You should use these basic rules to gain an understanding of how to correct color.

Basic color balancing with Levels

You can correct color casts in an image by using the Input and Output sliders in the Levels dialog to adjust the individual color channels. To edit an individual channel, go to the pop-up menu next to where it says ‘Channel’, mouse down here and choose a color channel to edit. Let's say you have a picture which looks too blue and you want to add more yellow (such as in the Figure 5.47 example below). If you select the Blue channel in the Levels adjustment and drag the gamma slider to the right, this will make the image more yellow. Another way to neutralize midtones in the Levels or Curves dialog box is to select the gray eyedropper and click on an area in the image that should be a neutral gray. With a levels adjustment, this action automatically adjusts the gamma setting in each color channel to remove the color cast. A Levels adjustment may be adequate enough to carry out basic image corrections, but doesn't provide you with too much control beyond reassigning the highlights, shadows and midpoint color values. The best tool to use for color correction is Curves, because with Curves you can change the color balance and contrast with a degree of precision that is simply not available with most other image adjustments.

Figure 5.47 With a photograph like the one shown on the left, it is not necessarily a bad thing to have a color cast, but let's say I wanted to apply a basic color correction to make it more yellow. If I add a Levels adjustment, I can select the Blue channel from the Channel menu and move the Input gamma slider to the right. This adjustment decreases the gamma in the Blue channel and makes the midtones in the image more yellow.

Color corrections in RGB

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