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Color and Light · entry 39 of 52
Afterimages appear when staring at a bright color fatigues the cone cells responding to that hue.
The longer version
Staring at a saturated colour keeps one cone type working hard while the others idle. The overworked cones adapt and reduce their output, so when the gaze shifts to a neutral surface the balance is temporarily skewed and the complementary hue appears. The fatigue is local, confined to the part of the retina that received the image.
The effect is called successive contrast and lasts only seconds. Opponent processing in the retina reinforces it, with red-green and blue-yellow channels arranged to signal differences rather than absolutes. Photographers and painters account for this when placing strong colours side by side, since prolonged viewing shifts how neighbouring areas appear.
Where this entry sits
These facts explore how light behaves and how human eyes turn it into the colors we see. Along the way you meet rainbows, prisms, mirrors, shadows, lasers, and optical tricks that fool our vision every day. The full list sits on the Color and Light page, where every entry is listed in order.
More From Color and Light
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Read 41Neon colors seem to glow because they reflect more light than ordinary dyes can.
Read 42Fluorescent materials absorb invisible ultraviolet light and re-emit it as visible color.
Read 43Glow-in-the-dark objects store light energy and release it slowly over several minutes.
Read 44Polarized sunglasses reduce glare by blocking light waves vibrating in one particular direction.
Read 45Soap bubbles show shifting colors because thin films interfere with reflected light waves.
Read 46Oil on wet pavement shows a rainbow pattern for the same reason thin soap films do.
Read 47A peacock feather gets iridescent color from microscopic structures rather than from pigment.
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