Film color appears as a transparent layer floating between eye and object; volume color deepens with fluid depth

Albers distinguishes two perceptual phenomena from surface color: (1) Film color — a thin apparent transparent layer between the eye and an object, independent of the object’s surface. Distant mountains appear uniformly blue regardless of their actual surface; the sun appears red at sunset; white ceilings near lawns appear green from reflected light. These are not surface properties — they float in perception. (2) Volume color — color existing within a transparent 3D fluid; perceived depth of color increases with the depth of fluid traversed. Coffee looks lighter in a thin column than in a cup. Swimming pools appear more saturated with depth. Both are physical phenomena (not purely psychological) exploitable in visual design.

Examples

Film color: atmospheric haze in GLSL (fog formula using depth buffer) simulates film color. Volume color: Beer-Lambert light absorption in water/glass shaders; Hydra’s feedback loops deepening color with each iteration.

Assessment

Identify one example of film color and one of volume color in the physical world. Then explain which is simulated when a GLSL fog function is applied and how you would simulate volume color in a 2D flat shader.