Chapter 5. Adjustment Layers

THIS CHAPTER LOOKS AT USING ADJUSTMENT LAYERS to apply the big guns of tonal and color correction, Curves and Hue/Saturation, to "select" parts of an image by sampling brightness values or colors. While Curves, Hue/Saturation, and other adjustment options are not selection tools per se, they let you target specific tones and colors; often they are more effective (and much faster) than actually making area selections. For example, to increase the contrast in an area of sky, you may need only to apply a Curves adjustment that targets the specific tones of the sky. To change the colors of the subject of an image, perhaps you don't need to select it first, but can instead sample the colors and make a Hue/Saturation adjustment.

Rather than use the options under the Image > Adjustments menu, which permanently change the pixels in your photo, it's preferable to use adjustment layers to apply changes on the layer above your image. With adjustment layers you get to make the omelet without breaking the eggsadjustment layers changes aren't permanently applied until flattening the image's layers, and you can change your mind as often as you like without damaging your pixels.

Effectively, this means unlimited undos. Compare this with Photoshop's other multiple-undos option, the History palette: you are limited to the number of history states you've set in the History palette, and, more importantly, they are only available until you've closed a document. An adjustment layer lets you change the adjustment at any timeweeks, months, or even years later. And because they leave your original image unharmed, adjustment layers make your workflow transparent: you can see exactly what's been done, especially if you name your adjustment layers to reflect what they do: for example, reduce blue, open shadows, lighten midtones, and so on.

There's more: In addition to letting you apply changes in a nondestructive way, each adjustment layer comes with a layer mask, which you can use (or not) to specify what parts of the layer are affected. Take the benefits of layers and combine them with the creative options of layer masks and you have some idea of what adjustment layers offer.