Citation

Ferree CE, Rand G. J. Exp. Psychol. 1929; 12(5): 363-391.

Copyright

(Copyright © 1929, American Psychological Association)

DOI

10.1037/h0071964

PMID

unavailable

Abstract

Among factors influencing the power to discriminate detail are: light intensity, visual angle, ratio of coefficients of reflection of object and its background, evenness of distribution of light, diffusion, angle of incidence, glare, etc. The present paper considers only the effect of change of intensity over a wide range on speed of vision in relation to size of work-object and difference in coefficients of reflection between object and its ground. Sizes varied from 1 to 5.2 minutes of arc, and coefficients of reflection from 16 to 78%. Illumination ranged from 1.25 to 100 ft. c. at the test surface. Instruments included the use of a Macbeth illuminometer, Ferree rotary tachistoscope, and the international test-object (broken circle). One subject (Rand) was used. The writers conclude that speed depends principally on size of object and differential reflection between object and ground. Largest effects occur in the lower range of the scale of intensity. These two variables are reciprocally related with intensity, and appropriate compensations are hence possible. The total relations among the variables studied which give speediest and surest discrimination are stated. (PsycINFO Database Record (c) 2012 APA, all rights reserved)