Why masks beat the eraser
A layer mask is a grayscale image attached to a layer — white reveals, black hides, gray shows partial transparency. Unlike the Eraser tool, a mask is fully editable: change your mind, paint white, and the pixels come back. Every modern Photoshop workflow is built on this single idea.
Creating and editing a mask
Select a layer and click the small rectangle-with-circle icon at the bottom of the Layers panel — that adds a white mask (everything visible). Hold Alt and click for a black mask. Then paint with a soft brush at 50% flow to blend edges naturally.
Mask from a selection
Make any selection — Quick Selection, Object Selection or Color Range — then click the mask icon. Photoshop converts the marching ants into a perfect mask. Refine the edge with Select and Mask: increase Smooth to soften jagged edges and Feather for soft transitions.
The five blending modes you'll use 90% of the time
Multiply darkens (great for shadows and ink). Screen brightens (perfect for glows and lens flare). Overlay and Soft Light add contrast and color richness. Color blends hue and saturation without touching luminosity — ideal for tinting black-and-white images.
Luminosity masks for compositing
Ctrl-click the RGB channel thumbnail to load a Lights selection — everything bright in the image. Save it as an alpha channel and use it to apply adjustments only to highlights. Subtract layers to isolate midtones; this is the foundation of professional landscape compositing.
Clipping masks
Alt-click between two layers to clip the upper layer to the shape of the lower one. Use this for non-destructive color grading on a portrait, or to fill text with a photo without rasterizing anything.
Group masks and nested masks
Mask a whole group to confine multiple adjustments to one subject. Combine a group mask with individual layer masks for fine control — a workflow used in every retouching, matte-painting and product shot pipeline.
Practice exercise
Open a portrait and a sky photo. Stack the sky on top, add a mask, and paint black over the model. Use Soft Light blending to merge the textures. In ten minutes you'll have produced a composite that would take hours with the eraser.