2. Psychophysics of vision

2.1 Visual trivariance

In contrast to previous research, which focused on objective results obtained in animals and then transposed to humans, we are now going to look at the subjective reactions of human beings confronted with the presentation of an image. If the image is particularly simple, reduced to the presentation of a uniform field, the observer will generally be able to describe three variables of the sensation produced, and only three, constituting the visual trivariance.

• Luminance: the observer will indicate whether he considers it to be low, medium or high, for example. It should also be noted that this is the only characteristic that can be analyzed in night vision, where colors are not detectable. If the image is more complex,...