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

The visual system serves various functions, four of which are discussed in the context of designing products.

  • Visual acuity is the ability to see fine details of objects
  • Contrast sensitivity is the ability to discriminate between different brightness levels
  • Colour perception is the ability to distinguish between different colours
  • Usable visual field is the ability to use the whole of the visual field to perceive detail in the area being looked at and the surrounding area
This mobile phone keypad appears clear with no impairment but its symbols and characters become difficult to decipher when viewed with reduced visual acuity.

A mobile phone viewed with no impairment, compared to the same phone viewed with reduced visual acuity

The subtle details of this mobile phone keypad are difficult to make out with reduced contrast sensitivity whilst the red and green coloured symbols become indistinguishable with red-green colour blindness.

Mobile phone seen with reduced contrast sensitivity and red-green colour blindness