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Selective Color Correction

Until now, you've worked on global color correction, but images can have different problems in different areas. Sometimes one part of the image will be fine and another area is way off color. Differing color casts can occur due to poor storage conditions, mixed lighting when the photo was originally taken, or misprocessing. Always start with the global color correction, and then select the problem areas that remain and apply local color correction.

Targeting the Problem Color

In figure 4.74, the color cast is rather subtle, but the lower blue readout in the Info palette reveals that the neutral tone of the studio background does have a yellow cast. Another way to see color casts is to look at the individual grayscale channels. Because the studio background is supposed to be neutral gray, all three color channels should have the same black density. As you can see in figure 4.75, the red and green channels are almost balanced with 66% and 68% density, but the blue channel is only at 54%. Wherever the channel is lighter, more light is allowed through, creating a color cast.

Figure 4.74Figure 4.74 The Info palette reveals a subtle yellow color cast.

Figure 4.75Figure 4.75 Checking the balance of individual channels.

At first I thought this would be a simple file to color correct; just add either a Curves or Levels Adjustment Layer, use the gray balance Eyedropper tool to click the neutral background to remove the color cast, and I'd be done. But after neutralizing the backdrop, I noticed that the young woman was still much too yellow (see figure 4.76), and the challenge remained to select only the yellow to achieve a balanced image, as shown in figure 4.77.

Figure 4.76Figure 4.76 The skin tones are too yellow.

Figure 4.77Figure 4.77 The final balanced image.

ch4_yellowport.jpg

  1. I added a Curves Adjustment Layer and clicked the studio backdrop with the gray eyedropper to neutralize the overall color cast. As you can see in figure 4.78, the young woman's skin is still too yellow.

  2. Figure 4.78Figure 4.78 Even after neutralizing the backdrop by clicking with the gray eyedropper, her skin tones are still too yellow.

  3. The yellow problem isn't on the Adjustment Layer, but rather on the Background layer. Always work on the layer that contains the problem, which in this case is the yellow cast remaining in the Background layer. Activate the Background layer.

  4. To select just the yellow components of the image, I chose Select > Color Range and selected Yellows from the drop-down menu, as shown in figure 4.79. The Color Range interface shows how Photoshop is making a selection mask that we can use in combination with any type of Adjustment Layer.

  5. Figure 4.79Figure 4.79 With the Background layer active, select the yellows with Color Range.

  6. Photoshop may pop up a warning box that says that no pixels were selected more than 50%. You can ignore this warning, because the selection will still be active. Photoshop just won't display the dancing ants!

  7. I added a Curves Adjustment Layer (see figure 4.80). In the Layers palette, a mask is automatically created from the Color Range selection. Wherever the mask is black, no color correction will take place, and wherever it is white or lighter, more color correction will occur.

  8. Figure 4.80Figure 4.80 Adding a Curves Adjustment Layer automatically creates a layer mask based on the selection.

  9. I switched to the blue curve (because blue is the opposite of yellow) and dragged it upward to remove the yellow color cast. Then I adjusted the green curve. Although these curve adjustments may look extreme, the mask makes the effect much more subtle, as seen in figure 4.81.

  10. Finally, to intensify the effect, I changed the Blending Mode to Multiply. Please note—you may not need to change the layer Blending Mode in all cases.

  11. Figure 4.81Figure 4.81 I adjusted the blue and green curves to remove yellow, and then changed the Blending Mode to Multiply.

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