Compound Layer Masks


Today’s Question: In a recent Ask Tim Grey response you described the capabilities within Lightroom Classic to create compound masks [for targeted adjustments]. Does Photoshop have these same capabilities and, if so, how does one use them?

Tim’s Quick Answer: Yes, Photoshop does support building composite masks for targeted adjustments (or composite images), through the use of multiple layer masks in conjunction with layer groups.

More Detail: In Lightroom Classic you can use one or more components to define a mask that determines which portion of an image will be affected by a targeted adjustment. This consists of adding to or subtracting from an initial mask using various other mask shapes. For example, you could create a mask for the sky, and then subtract the adjustment from the lower portion of the sky using a linear gradient.

In Photoshop you can create much the same type of effect, using a series of layer masks combined through the use of layer groups.

Of course, you could get started with the same basic concept by using selection tools. For example, let’s assume you had a photo showing three hot air balloons in the sky. You could create a selection of the first balloon, then use the “Add to Selection” option to create a selection of the second balloon. By then using the same “Add to Selection” option to select the third balloon, you would then have a selection that represented all three balloons. You could then add an adjustment layer based on that selection, for example, so that only the three balloons would be affected by the adjustment.

Layer groups provide a bit more flexibility. Let’s assume the same example of an adjustment that affects the sky, but in a gradient fashion. This can be accomplished with a composite mask created by combining multiple layer masks using layer groups. To get started, add two layer groups by clicking the folder icon at the bottom of the Layers panel, and then clicking that folder icon again.

Next you could select the sky by choosing Select > Sky from the menu. Then click on the thumbnail for the lower of the two layer groups on the Layers panel, and click the Add Layer Mask button (the circle-inside-a-square icon) at the bottom of the Layers panel. If you then add one or more adjustment layers to this layer group, those adjustments will only affect the sky in the image.

To refine that mask so that the sky is affected in a gradient fashion, click to select the upper layer group. Then click the Add Layer Mask button, choose the Gradient tool, and draw a white-to-black gradient from the upper portion of the sky to the lower portion. At this point the gradient mask layer won’t have any impact on the image because there is nothing inside that layer group. However, you can drag the lower layer group into the upper layer group, and now both layer masks will affect all adjustment layers in the lower layer group.

This is just one simple example, but it illustrates the possibilities of creating compound layer masks in Photoshop through the use of nested layer groups.