Controlling the visual space

Visual performance characterizes the precision and speed with which an individual performs a given visual task under specified conditions of speed, mental load, environment... The measurement of visual performance can only have statistical significance for a defined population sample. It is assessed by the success rate of a given visual task under specified conditions. It depends on a large number of factors, in particular :

• average luminance and retinal adaptation;

• exposure time ;

• detail/background contrast, luminance and color ;

• the angular dimension of the detail ;

• its position in relation to the visual axis;

• its sharpness, shape and orientation;

• luminance distribution in the visual field and the lighting system;

• the individual's history: visual education, level of training, motivation, type of work previously completed ;

• temporary or permanent abnormalities of vision, including, of course, those resulting from the subject's age...

The most important information on visual functions can be found in the Techniques de l'Ingénieur file [E 5 175] ("Signal processing and its applications" document base).

In this presentation, we will take up an approach based mainly on the work of the CIE. Although unfortunately still incomplete, this work is particularly useful in that it seeks to separate the intrinsic properties of the visual task from the overall result that they produce, for a given population, under given conditions, in terms of visual performance. They are also quite easily transposable to the understanding of concrete situations.

By their very nature, visual tasks possess, to varying degrees, the potential to be "read". This potentiality is modified by the environment and by the nature of the light falling on the visual task.

Furthermore, the visual task will only be usable by the observer to the extent that his or her visual capabilities are sufficient for the situation in question. Thus, any nuisances that may appear in the ergorama (glare, disruption of visual scans, etc.) must be eliminated, otherwise the visual task will be seriously impaired.

Finally, it should be noted that...