Preserving the Original with Adjustment Layers
An important point to remember about color correction is that you can apply it to the whole picture, to a selected single area, or to all but a selected area. When you apply a correction to the whole picture, it might improve some parts and make others worse, so you really need to look carefully at the end result and decide whether the good outweighs the bad.
Fortunately, there's an easy way to apply a correction and then change your mind. One of the best features of Photoshop is the capability to work in layers. (You'll learn all about layers in Hour 11, "Using Layers.") For now, you can think of layers as sheets of transparency film that you place over your image and paint or paste on. If you like what you do, you can merge the layers so that the additions become part of the image. If not, you can throw them away and try again. In addition to the layers that you paint on, Photoshop lets you apply adjustment layers. These work like normal layers except that instead of holding paint or pasted pictures, they hold the color adjustments that you make to the image.
There are a couple of ways to add an adjustment layer to your image. (This is Photoshop. You'll soon find that there are several ways to do almost anything you can think of.) First, and most logically, you can choose New Adjustment Layer from the Layer menu shown in Figure 5.15. They're also on a pop-up menu you reach by clicking a button at the bottom of the Layers palette (look for the button with the half-black, half-white circle).
Figure 5.15 The New Adjustment Layer submenu and the Layers palette.