Dissolve blend mode creates a grainy stochastic transition by randomly sampling pixels from each layer based on opacity

Dissolve is a special case: rather than blending per-channel values mathematically, it samples randomly from each layer. At 100% top layer opacity, all pixels come from the top. At 0%, all from the bottom. Intermediate values produce random pixel-level sampling with no anti-aliasing, resulting in a characteristically grainy, harsh appearance. Photoshop implements this with a pseudorandom noise dither pattern generated on startup. Dissolve cannot produce smooth gradients; it is used deliberately for its harsh, textural quality.

Examples

A Dissolve blend at 50% opacity produces a 50/50 random scatter of pixels from each layer. Unlike a Multiply or Screen blend, there is no smooth tonal interpolation.

Assessment

Explain why Dissolve at 50% opacity looks different from a Normal blend at 50% opacity, even though both give equal weight to each layer. What is the structural difference?