Afterimages in Colour Perception: Practical Relevance for Professionals

Colour professionals experience it regularly. After looking at a bright screen or intensely coloured samples for a long time, the neutral background suddenly looks different. These “ghost images” are afterimages, a fundamental aspect of the visual system that directly affects colour perception and assessment.

Afterimages arise from the way our visual system processes colour through opponent-colour processes. For colour professionals who need to make accurate colour assessments, understanding this mechanism is essential. It explains why colour matches sometimes appear to deviate under certain conditions and how surrounding colours influence perception.

The opponent-colour system as a foundation

The visual system does not process colour as isolated signals but through opposing pairs. Research shows that this process takes place at multiple levels, from the retina to the visual cortex.

In the retina, trichromatic signals from the cones are converted into opponent signals. Two main types are crucial: L-cones versus M-cones (red-green opponency) and S-cones versus the combination of L+M-cones (blue-yellow opponency). These systems are responsible for both high-resolution perception and colour discrimination.

The opponent principle means that certain colour combinations exclude one another. Reddish-green does not exist in perception, nor does bluish-yellow. When opponent channels are in balance, a neutral grey perception results.