V, W

Veiling luminance

Physiological glare is described through equivalent veiling luminance, which covers the visual detail reproduced on the retina like a veil and thus debases contrast and acuity. Equivalent veiling luminance leads to a limit value (threshold value) increment for the adaptation luminance necessary to recognize a visual detail (see also chapter “vision in old age”).

Unit: cd/m2

Visual acuity

Two points with a distance of A = 0.6 mm at a distance of B = 2.000 mm result in a visual angle of 1,03 angular minutes (1,03’). If said points can be recognised with certainty, that is referred to as a visual acuity of ca. 1. Visual acuity is the reciprocal value of the visual angle in angular minutes.

Visual acuity = 1/visual angle in angular minutes.

Visual angle in arc minutes = A/B, e.g. A = 0.3 mm and B = 2.000 mm result in a visual angle of 0,3/2.000 = 0,00015 arc minutes. Conversion to angular minutes is done as follows:

Visual angle in angular minutes = A ⋅ 360 ⋅ 60/(B ⋅ 2π) = 0, 52

An object at a height of 12 cm is seen from a distance of 100 m at a visual angle of 4 angular minutes.

Visual angle

see Visual acuity

Visual performance

Performance of the visual system (eye). Visual performance is described using the speed and accuracy with which a visual task is solved. Visual performance largely depends on the distribution of luminance – i.e. the impression of brightness which the eye gathers from a luminous or illuminated surface – and on visual acuity. Further influencing factors are the state of adaptation of the eye (adaptation to light or darkness), the visual object’s contrast compared to its surroundings, the size of the visual object and the speed of perception (the time span in which the visual impression can be processed). For ideal vision, the eye must be adapted to the ambient luminance and contrast as well as object size must be sufficient. Furthermore, the duration of perception is important, which, for example, makes fast-moving objects hard to recognise. With increasing age, visual performance decreases.

Visual task

Visually relevant elements of the work to be executed. The main visually relevant elements are the size of the object to be recognised, its luminance, its contrast with the background and its exposition duration.

Visual task area

The visual task area is the part of the workstation where the visual task is performed. The visual task may be horizontal, vertical or tilted. Where size and/or location of the visual task area are unknown, the portion of the work place where the visual task can occur must be assumed as the visual task area, and illuminated accordingly. This may necessitate that a larger portion of a work place, e.g. an entire manufacturing hall or a construction site, must be illuminated as a visual task area instead of individual workstations (see also chapter "Visual task areas").

Work place

Work places are:

  • work spaces in buildings including educational facilities,

  • outdoor workstations on facility premises, not including fields, forests and other lands belonging to an agricultural or forestry facility and are located outside of its area covered by buildings,

  • construction sites,

  • outdoor sales booths connected to retail shops,

  • water vehicles and facilities afloat on inland waters.

Work places include traffic zones; storage, machine and ancillary rooms; break rooms, on-call rooms, rest facilities and rooms for complementary physical exercise ; changing rooms, wash rooms and bathrooms (sanitary rooms); first-aid rooms.

Working area

Area within a room where a workstation or several workstations are located.


A workstation is the spatial area within a work place where the working task is executed. The workstation consists of:

  • the work surfaces, which can be horizontal, vertical or tilted, upon which the visual task is located,

  • the surfaces where the work equipment required for the task is located (e.g. tools, drawings),

  • the additional surfaces which are required for any user to perform the respective activities practicably and appropriately (e.g. standing, sitting and movement areas), and

  • storage areas required for the task (e.g. workpiece storage, file storage).