Lighten compares the colors you are painting with to the layer underneath and keeps the lighter color without blending them together.
The Math
The colors of the Lighten layer are compared pixel by pixel to the color of the base layer for each RGB channel. The higher number is selected, and since higher numbers mean brighter colors, the result can only get lighter (or stay the same) in this blending mode.
Mathier Math
Lighten uses the maximum function for each RGB channel:
Result = max(Top Layer, Base Layer)
For example, if the top layer has an RGB value of (80, 200, 150) and the base layer is (120, 160, 180), Lighten compares each channel:
- Red: max(80, 120) = 120
- Green: max(200, 160) = 200
- Blue: max(150, 180) = 180
The resulting color is (120, 200, 180).
Just like Darken, Lighten has three tiny comparisons happening for every pixel.
Core Rules of Lighten Mode
Black disappears: Pure black on the top layer has the lowest possible value, so it is always ignored, letting the base layer show through completely.
White wins: Pure white on the top layer has the highest possible value, so it completely replaces whatever color is underneath.
No color mixing: Like Darken, Lighten simply compares the two colors and selects the higher value for each RGB channel rather than blending them together.
When to Use It
Adding highlights: Paint bright streaks, highlights, or light effects on a Lighten layer and they will only affect areas where they are brighter than the underlying colors.
Blending textures: Lighten works well for textures, photos, or patterns with dark backgrounds, allowing the darker areas to disappear without manually erasing them.