Soft Light is a gentler, more diffuse version of Overlay. It lightens or darkens the colors underneath based on the brightness of the blending color, creating subtle contrast changes without the harsher effect of Overlay.
The Math
Soft Light uses the brightness of the blending color to determine whether to lighten or darken the base. Colors brighter than 50% gray brighten the base, while colors darker than 50% gray darken it.
Think of 50% gray as the neutral point: move lighter than it and the image gets brighter; move darker and the image gets darker. The difference is that Soft Light does this gradually, producing a much softer transition than Overlay.
Core Rules of Soft Light
50% gray is neutral: Painting with 50% gray has little to no effect on the layer underneath.
Light colors brighten: Colors brighter than 50% gray gently lighten the base.
Dark colors darken: Colors darker than 50% gray gently darken the base.
Soft contrast: The effect is more gradual than Overlay, making it less likely to produce harsh highlights or shadows.
When to Use It
Soft color grading: Tint a character or background with a subtle, unified color mood.
Glow and ambient light: Add gentle highlights or atmospheric colored light to skin, metal, cloth, or other surfaces.
Smooth shading: Add subtle shadow depth when Multiply or Overlay feels too strong or abrupt.