Effects of Patterning on Flicker Frequency

Abstract

Flicker was studied as perceived on a raster-scan CRT-based computer terminal in a typical use environment. The subject of the research was the relationship between the perception of flicker and the kind of spatial image presented. Both traditional images (filled white disks or squares) and images consisting of text and line drawings, similar in content to typical graphic computer terminal displays, were used in the study. This study measured the flicker perception of eight people. The most significant finding from this study was that CFF thresholds for some images presented on CRT displays in a typical use setting, differed significantly from more traditional images used in most CFF studies reported in the literature. For the eight images tested, the two which exhibited significantly higher CFF thresholds were lines or text on a black background (patterns 3 and 4). Therefore, an important factor to be considered in the prediction of the flicker characteristics of a 60 Hertz, noninterlaced CRT display in conditions similar to those of this study is the choice of normal video (black background) or reverse video format. The white background video format is likely to flicker when the display luminance is above 20 ft-L while the black background video format threshold was about 80 ft-L for both patterns 3 and 4. Alternatively, this luminance difference corresponds to about a 10 Hertz shift in CFF. In this study, the choice of video format alone, resulted in a luminance difference of 60 ft-L at CFF, or alternatively, resulted in a 10 Hertz shift in CFF at a particular luminance, for images normally found on actual CRT displays.