Bryn Mawr College monographs . g for a period of three minutes. In itself this test is notTABLE XX.—The Angi^k at Which the Light Fai^ls on the the effect on loss of efficiency of the angle at which the lightfalls on the work. Kind ofreflectionfrom read-ing pageduringwork period Foot-candles attest-card Hori-zon-tal Diflfuse Specular Work-ingdis-tance Diffuse 73 73Specular 73 73 Verti-cal Totaltimeclear 139 137137132 45 3-93-9 Total time blurred 41 43 4348 Time9 12 AM. 12 M. Totaltimeclear total time blurred 3-39 3-18 Maximaldistanceat which tes
Bryn Mawr College monographs . g for a period of three minutes. In itself this test is notTABLE XX.—The Angi^k at Which the Light Fai^ls on the the effect on loss of efficiency of the angle at which the lightfalls on the work. Kind ofreflectionfrom read-ing pageduringwork period Foot-candles attest-card Hori-zon-tal Diflfuse Specular Work-ingdis-tance Diffuse 73 73Specular 73 73 Verti-cal Totaltimeclear 139 137137132 45 3-93-9 Total time blurred 41 43 4348 Time9 12 AM. 12 M. Totaltimeclear total time blurred 3-39 3-18 Maximaldistanceat which test ob-ject canbe seen clear 89898989 Ratiosreducedto com-monstandard 3-0 analytical in principle. The results, as is stated above, are ex-pressed in terms of an aggregate loss of function. The con-tributive factors may be inferred from the nature of the test, but CHART v.—The Angle at Which the Light Fai,i,s on the Work. Showing the effect on loss of efficiency of the angle at which the light falls on the 2 3 4- the test is not in itself designed to separate them out. Andindeed it is a question whether any practical good can accrue tothe practise of lighting from a knowledge of just what part oi TRANSACTIONS OF ILLUMINATING ENGINEERING SOCIETY 486 the visual apparatus it is that falls off in function as the resultof an unfavorable condition of lighting. Obviously the chiefneed is to find out what are the conditions that cause the eye tolose its ability to see clearly and to avoid these conditions inplanning and installing a lighting system. From the beginningwe have had in mind, however, an analysis of effect. Our testsfor the sensitivity of the retina showed, for example, that verylittle, if any, of the difference in results we have gotten for thefour types of lighting we have employed can be ascribed to aloss in the efficiency of the retina, or the light sensitive part ofthe visual apparatus. Three sets of factors are involved in clearseeing: (i) the se
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