The optic nerve runs from the back of the eyeball into the visual cortex of the brain. It receives electrical signals from specialized cells (called photoreceptors) attached to various parts of the retina. The retinal image -- the optical pattern that falls onto the retina in the form of light rays -- is converted into electrical signals by photoreceptors. (The term "image" will reappear with different meanings in the course of this discussion, but it always refers to an informative pattern of light, neural activity, or experience that starts with the light provided to the eye by the scene being looked at.)
When the signals reach the brain, they are interpreted as visual images. Whether the images are interpreted as clear /blurry or colored/monochrome depends on which photoreceptors transmitted the signals. This, in turn, depends upon which part of the retina that the light rays that form the image actually fall onto. If the image falls onto the fovea, it will be clearest and its color most vivid and accurate. (This happens when you look directly and squarely at something.) The further outside this area the image falls, the more indistinct it will be. (This happens when you catch sight of something out of the corner of your eye.) Bonnard was very interested in the variations in optical acuity owing to the different ways that the eye receives and processes imagery.
| ©1998 The Museum of Modern Art, New York |
 |