Evening Republican, Volume 59, Number 73, Rensselaer, Jasper County, 28 March 1917 — Why One Can See Better in Moderate Than Bright Light. [ARTICLE]

Why One Can See Better in Moderate Than Bright Light.

An observant chauffeur, passing nn automobile with glaring headlights, noted that objects at the side of tttfe road which had been distinctly visible dropped out. of sight when the bright. them. Since one can see better in a little irgfit“ihau in no light, he wondered, why can one pot see better in bright light than in moderate light? The answer is, paradoxically, that -the less light there is the better one sees, for the brighter the object the less efficient is the eyesight. Ts, after we have been in darkness, we suddenly turn on a bright light and look at our eyes, in the mirror, we can see the pupil of the eyerapidly growing small,>r. If we reduce the light the pupil dilates again. What happens Is the same as In the camera when we adjust the shutter to the intensity of the light. The colored iris of the eye corresponds to the shutter. It consists-chief-ly of a muscle which, as the light increases, is stimulated to contract, thus drawing the curtain and shutting out some of the superfluous light. It usually takes at few seconds for this adjustment to take place. Thus when we emerge from darkness into light we are blinded until the iris can shut out some of. the light from the eyes. ■