by Julieanne Kost
Clipping masks are most commonly used when an adjustment needs to be applied to a single layer in a multi-layer document. For example, if you have a triptych of images (each on their own layer) within a single document and need to brighten only one of the images, you can add an adjustment layer and “clip” it so that it only effects that single layer.
The easiest way to “clip” an adjustment layer to the layer below it is to target the layer that needs the adjustment in the Layers panel, then click the clipping icon at the bottom of the Adjustment panel before adding the adjustment, (or, if you forget, you can click the clipping the icon after adding the adjustment at the bottom of the Adjustment panel). As you make the adjustment, you will notice that the modification is only effecting the layer that the adjustment is “clipped” to.
Another use of clipping masks is to clip content suce as a photo to a shape such as type. In order to do this, put the type layer under the photo layer on the Layer’s panel, target the type layer (by clicking in it in the Layer’s panel) and select Command-Opt (Mac) / Control-Alt (Win) + G to create a Clipping Mask.
Or, on the Layers panel, hold the Option (Mac) / Alt (Win) key and position the cursor over the line that separates the two layers in the Layer’s panel. When you see the icon switch to a triangle with two overlapping circles -click to create a Clipping Mask.
You can have multiple layers clipped to a base layer. Visually, you will know that the layers are clipped because the bottom most layer’s name will be underlined in the Layers panel, and the clipped layer(s) will be indented with an arrow pointing downwards towards the base layer.