Vision

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Overview | Understanding vision | Visual functions (5) | Env. context | Design guidance (2) | Pop. stats. (2)

Visual functions

Introduction | Visual acuity | Contrast sensitivity | Colour perception | Usable visual field

Colour conveys information about the physical world. Loss of colour discrimination (or colour blindness) is the inability to distinguish between various colours. The notion that people with colour blindness cannot perceive colour is inaccurate, and in fact total loss of colour perception is extremely rare. A person who is colour blind cannot effectively distinguish between different colours in the colour spectrum.

The most common form of colour blindness is red-green colour blindness, where the ability to distinguish between colours from red to green in the colour spectrum is reduced. These colour confusions can make interaction with products difficult if colour alone is used to provide information.

The diagram opposite shows various foreground and background colour combinations (top) and the corresponding simulated appearance for a red-green colour blind person (bottom). Note that images that have similar brightness contrasts can disappear when viewed by someone with colour blindness.

The word design is repeated in a variety of colours, on various coloured backgrounds.

In order to determine which colour combinations are most effective, try viewing this image at various distances from your eyes and squinting as you read it

The word design is indecipherable under red-green colour blindness simulation when red and green have been used as contrasting colours. Under simulation, both red and green become brown, whereas black, white, yellow and blue remain unchanged.

The same images viewed with a simulated red-green colour blindness.