Scotopic And Photopic Vision
August 5th, 2005 | No Comments »The following text is abstracted from Wikipedia:
“Scotopic vision is the monochromatic vision of the eye in dim light. Since cone cells are nonfunctional in low light, scotopic vision is produced exclusively through rod cells. Vision in normal light with functioning rod cells is photopic vision”.
That “cone cells are non-functional (or shutdown)…” there is just no experimental evidence for such a statement! One would reason this way if one believed that cone cells are the source of color…which they, clearly in this explanation, are not! “Scotopic vision is produced exclusively through rod cells”… how on earth? …invoking what mechanism? Scotopic and photopic vision are therefore presented as two separate systems. What physical evidence is there for this statement? From the viewpoint of my geometric explanation all of this is completely erroneous and leads one down the wrong path of thought… and has done so for years and years! It attempts to explain phenomenologically the behavior of the vision process but, in fact, using the completely wrong mechanisms.
The correct definitions for these terms (if the terms must be used at all):
Scotopic vision: “under low light level conditions the rod cells of the peripheral retina act together (and there is experimental evidence of this) as a “light meter” using the exact short wavelength limit of visual response to control pupillary constriction dilating the pupil of the eye and controlling the admittance of light to the retina. Under these conditions there is still insufficient light intensities of the three primary RGB wavelengths falling on the the retina to activate the “Land color mechanism”, i.e., insufficient light intensity incident on either side of the geometrically determined mid-band (550 nm) reference point at 7-8 degrees of retinal eccentricity. The colorless image that is perceived results from long wavelength radiation falling on the central all-cone fovea.”
Photopic vision: “under normal, i.e., daylight, levels of illumination the three primary RGB light intensities abstracted by the retina are sufficient to activate the “Land color mechanism” as defined above and the image including the hues of color is perceived. Peripheral rods, acting together and determined by the short wavelength end of the visible spectrum, constrict the pupil thus controlling the intensity of light entering the eye as necessary”
