Photoshop CS4 Studio Techniques- P6

Photoshop CS4 Studio Techniques- P6: Staring at a shelf full of Photoshop books at the localbookstore, it seems that there are more special-effect“cookbooks” and technical tomes than anyone would evercare to read. The problem is that none of those “cookbooks”provide enough detail to really let you feel like youunderstand the program
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Photoshop CS4 Studio Techniques- P6Chapter 3 Layers and Curves First, you can apply Curves to the active layer by choosing Image > Adjustments > Curves. Immediately after apply- ing Curves, you can choose Edit > Fade Curves and set the Mode pop-up menu to Luminosity (Figure 3.108). The Figure 3.108 Choose Edit > Fade Fade command limits the last change you made (Curves, Curves to limit changes to the bright- ness of the image. in this case) to changing only the brightness of the image. (Luminosity is just another word for brightness.) It won’t shift the colors or change how saturated they are. Your other choice would be to apply Curves to more than one layer by clicking the Curves icon in the Adjustments panel. Then you can change the blending mode in the Layers panel to Luminosity (Figure 3.109). An adjustment layer affects all the layers below it but none of the layers above it. It’s also a nonpermanent change, because you can double-click the adjustment layer thumbnail in that layer to reopen the Curves dialog and make changes. There- fore, any Curves techniques you use for adjusting grayscale images will work on color images if you use the Luminosity blending mode (Figure 3.110). Figure 3.109 You can quickly apply a Curves adjustment as a separate layer by clicking in the Adjustments panel. Figure 3.110 With a Curves adjustment layer, you can make non-destructive changes to an image. Color shifts aren’t the only problems you’ll encounter when adjusting color images with Curves. The mode your image is in might have an adverse effect on the adjustment. RGB color images are made from three components (red, green, and blue). A bright green color might be made out of 0 red, 255 green, and 128 blue. When you first open the136 II: Production EssentialsCurves dialog, the pop-up menu at the top of the dialog isset to RGB, which will cause any points to affect the sameR, G, and B values. Clicking that green color in the imagedisplays a circle at 165 on the curve, which will affect allthe areas that contain 165 red, 165 blue, and 165 green.Equal amounts of R, G, and B create gray. Simply clickingthe curve of a color image usually causes the colors to shiftin an unsatisfactory way, because the circle that appearswhen clicking the image will not accurately target the areayou clicked.While working in RGB mode, all color areas shift becausetheir RGB mix changes as the Curves dialog shifts the RGBvalues in equal amounts. Ideally it would affect only theexact mix of RGB from which the color is made, but Curvesdoesn’t work that way in RGB mode. The solution to thisproblem is to convert the image to LAB mode by choos-ing Image > Mode > Lab Color. In LAB mode, the image is The word LAB in LAB mode is anmade from three components: Lightness, A, and B. When acronym for what color channels ityou adjust the image, the Curves dialog automatically sets controls: Lightness, A, and B. Don’titself to work on the Lightness information, which prevents say “lab,” say the letters: “L-A-Bthe adjustment from shifting the color of the image and mode.”makes the circle show up in the correct position for accurateadjustments. When you’re done with the adjustment, youshould convert the image back to RGB mode, because manyof Photoshop’s features are not available in LAB mode. Youmay not use LAB mode for every color image; reserve it ...