Layer blend modes are non-destructive and dynamic; painting tool blend modes permanently alter pixels

There are two contexts for blend modes: layer blending and tool blending. Layer blending applies the mode dynamically between two layers — no pixels are changed, only the visual result. The mode can be changed or removed at any time. Tool blending (e.g. Photoshop brush set to Multiply) calculates the blend at the moment of the stroke and permanently writes the result into the layer’s pixels. After the stroke, the blend is baked in and cannot be adjusted (only undone). This distinction matters for workflow: layer blends enable non-destructive compositing; tool blends enable organic, accumulated build-up on a single layer.

Examples

Using a Screen-mode brush at low opacity to paint light into a shadow area: each stroke accumulates screen-blended light organically on one layer, without needing a separate glow layer.

Assessment

A photographer wants to add vignetting non-destructively so they can adjust the strength later. Should they use layer blend mode or tool blend mode, and why?