How to Master Layer Masking for Compositing

A layer mask controls the transparency of a layer without deleting any pixels. White on a mask reveals the layer, black hides it. Gray creates semi-transparency. This non-destructive approach means your original image is always safe — you can paint on the mask endlessly without damaging the pixels underneath.

Open two images you want to composite together — for example, a person cutout and a scenic background. Place the person layer above the background. With the person layer selected, click the 'Add Layer Mask' icon (rectangle with circle) at the bottom of the Layers panel. A white thumbnail appears next to your layer — this is your mask.

Press B to select the Brush Tool. Set your foreground color to black by pressing D (resets to default black/white) then X if needed. With black selected, any area you paint on becomes transparent — like erasing, but non-destructively. The mask thumbnail shows where you've painted as black areas. Start painting around the edges of your subject to blend them into the background.

Press X to swap foreground colors — now you're painting with white. White on the mask reveals the layer. If you accidentally hide too much of your subject, simply paint with white to bring it back. This back-and-forth between black and white gives you total control. Think of it like sculpting: black chips away, white adds back.

For realistic compositing, use a soft brush (hardness 0%) for edges that should blend naturally — like adding shadows or fog. Use a harder brush (hardness 50-80%) for defined edges. Adjust brush opacity (30-50%) for gradual reveals. The key to professional compositing is varying brush hardness and opacity to match the natural edge quality of each element in your scene.