Layer Mask: Tip for editing Masks in Photoshop
Tips & Tutorials, by Mark White
January 14, 2013
Layer masks can be viewed in a number of ways. Here’s a tip when working with them in Photoshop
Edit a layer mask at any point by holding Opt/Alt and clicking on its thumbnail in the Layers palette.
The mask will be transported on to the image itself, and show up as black and white, onto which you can use the Brush and Eraser tools to edit its outline directly.