If you spend any significant amount of time working with masks, get to know the Masks panel (see Figure 8-9). Editing masks to get them just right has traditionally involved various power-user techniques. Like the Refine Edge dialog (discussed earlier in this chapter) and the Adjustments panel, the Masks panel is another example of how related features in Photoshop have been simplified and consolidated from a task-oriented point of view. For example, instead of having to control mask density by using the Output Levels sliders in the Levels dialog, all you have to do now is yank the Density slider in the Masks panel.
Figure 8-9 The Masks panel
Up to this point I've been talking about pixel masks that are made up of pixels, but the Masks panel also accommodates vector masks made up of paths (see Figure 8-10). When you click the Pixel Mask or Vector Mask button in the Masks panel, the current layer gets a new mask of that type if it doesn't already exist for that layer.
Figure 8-10 Pixel and vector masks
Pixel Masks. When you click the Pixel Mask button in the Masks panel, a new pixel mask is added to the current layer, if it doesn't already have one. Use any painting tool to create black (transparent), white (opaque), and gray (semitransparent) areas in a pixel mask. The Masks panel provides these controls for a pixel mask:
- Density. Use this option to change the opacity of the mask so that you can control it independently of the layer opacity. Sure, you were able to do this in Photoshop CS3 and earlier by applying an image adjustment such as Levels to the mask, but repeated adjustments would degrade the mask. The Density slider is better because it's nondestructive—you can easily dial it back at any time.
- Feather. This option controls the softness of the mask edges. This nondestructive option lets you freely adjust edge blur without having to apply a blur filter.
- Mask Edge. This button is the same as the Refine Edge feature discussed earlier in this chapter; it fine-tunes the edge of a selection. Because selections and masks are two forms of the same thing, it's as helpful to have Refine Edge in the Masks panel as it is to have it in the Options bar for selections.
- Color Range. This option is good for creating a mask if you just added one and you need to isolate an area by color. I discuss Color Range in Chapter 9.
- Invert. This option exchanges the opaque and transparent parts of a mask so that you can choose to paint the masked area with black or white and just swap those colors later. It's yet another shortcut to the Image > Invert command, which you can also get by pressing Command-I (Mac OS X) or Ctrl-I (Windows).
Vector Masks. This type of mask is defined by paths you draw and edit using the Pen tool and shape tools (see Chapter 11, "Essential Image Techniques"). Areas outside the path are transparent, and areas inside it are opaque. Although a vector path is hard-edged by nature, you can use the Feather slider to apply a nondestructive feathered edge to a vector mask—this was not possible in earlier versions. The only other option for vector masks is Density. To make any other kind of change to a vector mask, you must either edit its path using the Pen tool group or convert its path to a selection or channel so that you can edit it as a selection or as pixels, respectively.
Clipping Masks. A clipping mask lets a layer act as a mask (see Figure 8-11). In the Layers panel, select one or more layers directly above the layer you want to use as a mask, and press Command-Option-G (Mac) or Ctrl-Alt-G (Windows), the keyboard shortcut for choosing Layer > Create Clipping Mask. You can also Option-click (Mac) or Alt-click (Windows) the dividing line between the base layer and the higher layers you want it to clip.
Figure 8-11 Using a layer as a clipping mask
The Adjustments panel offers a clipping mask button, which can be confusing because it appears in two different ways. When no adjustment layer is applied, the button controls whether new adjustment layers are added as clipping masks. When an adjustment layer is selected (you see its controls in the Adjustments panel), the button appears near the middle and controls whether that specific layer acts as a clipping mask (see Figure 8-12).
Figure 8-12 The clipping mask buttons in the Adjustments panel
Viewing Masks. If you want to see only the layer mask (see Figure 8-13), Option-click (Mac) or Alt-click (Windows) on the layer mask's thumbnail in the Layers panel. This is most helpful when touching up areas of the layer mask (it's sometimes hard to see the details in the mask when a background image is visible). You can disable (hide) a mask by Shift-clicking a mask thumbnail or clicking the Disable Mask button in the Masks panel (see Figure 8-9); when you do this, a red X appears in the mask thumbnail in the Masks and Layers panels.
Figure 8-13 Mask views of the image that was shown in Figure 8-10
If you want to see the mask as a transparent overlay over the image, press the backslash key (\). If you're editing an adjustment layer, make sure you only tap the backslash key, since holding down that key displays the state of the image before the current adjustment (a before-and-after comparison).
Copying Layer Masks. To copy a layer mask, in the Layers panel Option-drag (Mac) or Alt-drag (Windows) the layer mask thumbnail to the layer where you want to apply the mask.