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Technical environment
Technical environment
Global standard 220V-240V/50Hz-60Hz
Standard for USA/Canada 120V/60Hz, 277V/60Hz
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Visual performance: Definition—simply explained

Person making notes at a desk – this visual task requires increased visual performance.

Visual performance is the ability to perceive and identify objects or small details and visual tasks which have low contrast to the surroundings.

Overview on the topic visual acuity

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What does visual performance mean?

Visual performance is the term used to describe the perceptual performance accomplished by the eye. The difficulty of a visual task increases upon reduction in color- or luminance contrast and detail size.

An example: the lower the color- 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 fulfill the visual task required (e.g. reading, writing or drawing).

What influences visual performance?

The brighter it is, the higher our visual performance. At an illuminance (measured in fc (or lx)) of 1.86 fc (20 lx), we can only just distinguish people's facial features. Simple work, such as meetings in conference rooms, already needs at least 18.56 fc (200 lx), whilst complicated visual tasks, such as control tasks or precision assembly, require up to 185.81 fc (2,000 lx). Illuminances of even up to 929.03 fc (10,000 lx) are required in special cases such as operations in hospitals.

Fundamentally, visual performance increases abruptly with increasing illuminance. However, above 92.90 fc (1,000 lx) it increases only slowly to then finally decrease at very high illuminances due to the occurrence of glare.

Graphs depict various changes in visual performance

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 18.6 fc to 92.9 fc (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.

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Further topics on seeing and perceiving

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