Abstract

Critical flicker frequency (CFF) was measured as a function of luminance and field size in dichromats. The field sizes were 0.7°, 1.1°, 1.6°, 2.3°, 3.7°, and 5.5°. For a given field size, a 580-nm square wave alternation was presented from –0.35 to 4.65 log trolands in 0.5 log unit steps. The observer adapted to each luminance level for 1 min after which three descending (fusion to flicker) thresholds were collected. The median was plotted as a function of luminance. The CFF vs luminance functions for each field size were averaged separately for deuteranopes and protanopes. For both classes of dichromats, increasing field size resulted in systematic increases in CFF. For each field size, the deuteranopic and protanopic data sets could not be matched with a translation along the luminance axis, indicating the difference between the two groups is not due to the choice of 580 nm as the test wavelength. All curves showed an asymptote at high luminances which occurred consistently at a higher frequency for deuteranopes than protanopes (e.g., for the 0.7° field, the asymptote was ~45 Hz for deuteranopes and ~35 Hz for protanopes). These data are compared with other literature reports of flicker sensitivity of dichromats.

© 1986 Optical Society of America