Download or read book Experimental Study of the Effects of Surround Brightness and Size on Visual Performance written by Fred H. Ireland and published by . This book was released on 1967 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: A visual display must often be used in a setting where the surrounding visual field is brighter than the background area within the display. Such use violates a common human factors recommendation that the brightness of the display surround should be equal to, or slightly less than, that of the background in the display itself. The purpose of this experiment was to determine, quantitatively, the degradation in visibility due to high surround brightness and thus to provide useful data for the display system designer. Measurements were made of the target-to-background contrast required for each of 5 Ss to determine, with 50% accuracy, the orientation of a light Landolt ring target centered on a darker circular background. The target gap subtended 1.93 minutes of arc. Background angular subtense was varied from 5° to 45°, background brightness from 0.17 to 18.43 millilamberts and surround-to-background brightness ratio from 0:1 to 100:1. A uniform surround, independently variable in brightness with respect to the background, filled the rest of the visual field. The scene was viewed monocularly with natural pupil. The contrast limen was found to vary directly with surround-to-background brightness ratio for ratios greater than one. The variation with background size was smaller than predicted by an equation for integrating the effects of point sources of glare. An apparent tendency for a slight increase in limen as the surround-to-background ratio decreased from 1:1 to 0:1 was not statistically significant. Results are described by equations, and a procedure for their practical application is illustrated.