Fovea

source: Étienne Tisserand, Jean-François Pautex, Patrick Scweitzer, ANALYSE ET TRAITEMENT DES SIGNAUX, Méthodes et applications au son et à l’image, Dunod,

Paris, 2008.

traduction: doxa-louise.

Color Perception

The visual perception of a  luminous stimulus can be decomposed into two sensations:

• a luminous sensation tied to the intensity of the observed stimulus;
• a color or chromatic sensation depending on the luminous spectrum of the stimulus.

These sensation are transcribed to the brain by the two types of visual receptors found in the retina:

-rods adapted to the sight of forms and mouvement. These are active under conditions

of low lighting (scotopic vision);

• cones adapted to the sight of colors and details under medium to high lighting conditions (photopic vision or daylight).

As a consequence, only the cones are responsible for the color sensation. The density

of cones is particularly high in the central zone of the retina called the fovea, whose

average width is approximately 0,4mms. As one leaves the retina, the proportion of rods

goes up to the detriment of that of cones which are pratically absent at the periphry of the retina. The spectral band of light, visible by the human eye, ranges in wavelength

between 380 nms and 780 nms. In order to analyse this band, 3 types of cones of a

specific spectral sensibility are active.