Visual performance is the ability to perceive and identify objects or small details and visual tasks which have low contrast to the surroundings.
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Visual performance is the ability to perceive and identify objects or small details and visual tasks which have low contrast to the surroundings.
An example: the lower the colour- or brightness contrast between printed text and a sheet of paper, the more difficult it is to read the text. The same applies to small font sizes.
What is the difference between visual performance and visual task? The visual performance must be accomplished by the eye as the visual organ, so that the person can fulfil the visual task required (e.g. reading, writing or drawing).
Fundamentally, visual performance increases abruptly with increasing illuminance. However, above 1,000 lx it increases only slowly to then finally decrease at very high illuminances due to the occurrence of glare.
1. Visual acuity S according to age (nominal values)
2. Influence of illuminance E on visual acuity S of normal-sighted observers
3. Influence of illuminance E on relative visual performance P for simple (upper curve) and difficult visual tasks (lower curve)
The guideline values for illuminances at workplaces, as specified primarily in EN 12464, range from 200 to 1,000 lx within the framework outlined above. Recommended illuminances in individual cases depend primarily on the size of the visual task and its contrast with the immediate surroundings, whereby very small, low-contrast visual tasks require the highest level of illuminance.
