1. Visibility potential of a visual task as defined by the CIE

1.1 Visual reference tasks

A detailed description of the work carried out by the CIE (Commission Internationale de l'Éclairage) can be found in publications 19, 19/2.1 and 19/2.2. The most important concept adopted by the CIE is undoubtedly that of equivalence to the visibility threshold, since it is in relation to this threshold that the visibility level of a visual task can be defined.

Let's briefly review the principle of threshold visibility, based on the fundamental experiment that serves as a reference in this field. The CIE defines a relative contrast sensitivity curve (RCS _Réf ) which is deduced from the threshold contrast values obtained from a simple experiment: 4 arc-minute luminous discs, presented close...