Contrast Sensitivity of the Human Visual System at One Luminance Level While Adapted to a Stimulus at Another Luminance Level
AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH SCHOOL OF ENGINEERING
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This report documents an investigation of the hypothesis that the organization of the receptive fields in the human visual system changes to compensate for changes in the average luminance of the visual stimulus. Foveal measurements of contrast sensitivity to sinusoidal spatial frequency were made at one luminance level while the subjects were adapted to a spatial sinusoid of a different average luminance. The luminance levels used were 3.65 and 35.5 ft- lamberts. Contrast sensitivity curves were generated for the range of spatial frequencies from 2 through 11 cycles per degree for adapting spatial frequencies of 4, 6, and 8 cycles per degree. Adaptation and testing at the same average luminance level produced a depression in the contrast sensitivity curve centered over the adapting spatial frequency. adapting to a low luminance level stimulus and testing at a higher luminance level produced a shift in the adaptation depression to a lower spatial frequency. adapting to a high luminance level and testing at a lower luminance level produced a shift to a higher spatial frequency. The shift in the adaptation depression was observed for red, green, blue, and white light stimuli and was observed for the unadapted eye of a subject whose other eye was adapted.
- Anatomy and Physiology
- Human Factors Engineering and Man Machine Systems