Editing the layer mask of adjustment or fill layers

A layer mask protects sections of a layer (or the entire layer) from being edited, and can be used to show or hide sections of an image or layer effect. When the layer mask is attached to an adjustment layer, it's used to control which areas of the underlying layers are affected by the adjustment layer. When the layer mask is attached to a fill layer, it's used to define the area that's filled in the fill layer.

You can edit the mask of an adjustment layer or fill layer. If you made a selection before you added the adjustment or fill layer, a mask is automatically created for the selected area. If you didn't select an area beforehand, all areas of an adjustment or fill layer are "unmasked".

Editing a mask involves painting or erasing with black, white, or shades of gray. When you select an adjustment or fill layer in the Layers palette, the color swatches in the toolbox are black and white. To add to the mask, paint with black or erase with white. The mask defines areas that aren't affected by an adjustment or fill layer. To subtract from the mask, paint with white or erase with black. Subtracting from the mask increases the area affected by an adjustment or fill layer. Painting or erasing in shades of gray will remove areas from the mask and add areas to the mask in various levels of transparency.


Adjustment layer with triangular mask added

To edit the layer mask for an adjustment or fill layer:

1. Select the adjustment layer or fill layer in the Layers palette.
2. Select the paintbrush tool, or any painting or editing tool.
3. Use the following methods to view the layer mask:
• Alt-click (Windows) or Option-click (Mac OS) the layer's leftmost thumbnail to view only the grayscale mask. Alt/Option-click the thumbnail again to redisplay the other layers.
• Hold down Alt+Shift (Windows) or Option+Shift (Mac OS), and click the layer's leftmost thumbnail to view the mask in a red masking color. Hold down Alt/Option+Shift and click the thumbnail again to turn off the red display.
4. To constrain editing to part of the mask, make a selection. (See Selecting pixels.)
5. Edit the layer mask:
• To remove areas of the adjustment effect or fill, paint the layer mask with black.
• To add areas to the adjustment effect or fill, paint the layer mask with white.
• To partially remove the adjustment effect or fill so that it shows in various levels of transparency, paint the layer mask with gray. (Double-click the foreground color swatch in the toolbox to choose a gray shade in the Color Picker.) The extent to which the effect or fill is removed depends on the tones of gray you use to paint. Darker shades are more transparent; lighter shades are more opaque.

Shift-click the mask thumbnail (the layer's rightmost thumbnail) in the Layers palette to turn off the mask; click the thumbnail again to turn on the mask.