The physiology of vision with special reference to colour blindness (1920)
Edridge-Green, Frederick William, 1863- · London, G. Bell and sons · leaf 96
VARIOUS VISUAL PHENOMENA 81 object occupying a known visual angle on the sky above a house. A comparison is easily made in both cases with portions of the house. If an observer look straight at the cloudless sky, preferably about three hours before the siin sets, for about ten to twenty seconds, a… … Fig. 4. each diameter, and this surrounds a central brighter portion which corresponds to the point of direct vision. This is about 40 to 50 minutes in diameter and is circular in form. (See Fig. 4.) Helmholtz ^ gives a disc of the diameter of about 40 to 50 minutes as the apparent size of the…
Color vision · Vision · Color blindness · Refraction · Ophthalmology
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