Psychophysics of reading IV Wavelength effects in normal and low vision

Abstract

Does the color of text influence its legibility? There are reasons why it may do so for specific groups of low-vision observers. We used psychophysical methods to measure the effects of wavelength on the reading performance of four normal observers, two dichromats, and twenty-five low-vision observers. Reading rates were measured for text scanned across the face of a television (TV) monitor. We compared performance under four luminance-matched conditions in which sets of neutral-density and Wratten color filters were placed in front of the TV screen--blue (lambda max = 430 nm), green (lambda max = 550 nm), red (lambda max = 650 nm), and gray. Under photopic conditions, the reading rates of normal subjects were independent of wavelength, with the exception of characters near the acuity limit. At lower luminances, wavelength effects could be explained by the shift from photopic to scotopic vision. It was hypothesized that light scatter or absorption in eyes with cloudy ocular media would result in depressed performance in the blue. Only one of seven subjects demonstrated this effect, which we traced to wavelength-specific absorption. Observers with advanced photoreceptor disorders tended to read blue text faster than red text. This could not be explained on the basis of photopic spectral sensitivities alone. Finally, the presence of central or peripheral field loss was not predictive of wavelength-specific effects in reading. On the whole, wavelength only occasionally plays a significant role in reading. When it does, performance tends to be depressed either in the red or the blue and to be nearly optimal for green or gray.

The impact of color combinations on the legibility of a Web page text presented on CRT displays

“…There was a strong positive correlation between this measure and the logarithm of the luminance contrast. The hypothesis that reading ability is sensitive to luminance contrast and insensitive to chromatic contrast was also supported by the results of Legge and Rubin (1986). They measured the reading rate of four color combinations always with black as background and four different chromaticities as text color.…”

The influence of color on transient system activity: Implications for dyslexia research

“…Psychophysical evidence in normal and dyslexic readers suggesting that transient activity is attenuated by red light has been demonstrated in measures of metacontrast (Breitmeyer & Williams, 1990;Williams et al, 1991) and stroboscopic motion (Breitmeyer & Williams, 1990), whereas other studies have demonstrated no effect of red stimuli (e.g., Breitmeyer & Breier, 1993;Solman, Cho, & Dain, 1991). Similarly, in measures of actual reading performance, found a decrease in reading comprehension when using red overlays on text with reading-disabled children, but they found no difference between red and gray overlays in normal readers; however, other studies have again demonstrated no effect of red stimuli (e.g., Legge & Rubin, 1986). Similar conflict exists regarding the influence of blue light on transient activity and reading ability.…”

Adaptive luminance contrast for enhancing reading performance and visual comfort on smartphone displays

“…The results were contrary to earlier research results stating that reading speed is fastest when the luminance contrast between text and background is maximal. 24,25 In terms of visual comfort, subjects felt most comfortable under the default stimulus (D100). Comparing visual comfort among two stimuli in same set and the default (D100, T70, and T40; D100, B80, and B70; D100, TB70, and TB40), visual comfort decreased rapidly in every set when the luminance contrast became smaller.…”

“…Brainwave data were measured for 5 min and 10 s, and the first 10 s of the recorded data were deleted to improve the accuracy of the results. The collected data were converted by 256-Hz sampling frequency and 12-bit analog-digital converter, then saved through Telescan, the analysis program developed by Laxtha Inc. After that, the relative ratio of the high beta rhythm (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) 26 to the entire range (3.5-50 Hz) was then calculated using the data. A high beta rhythm is generated when people feel stress and anxiety; 27 thus, a low ratio of high beta rhythm indicates that the subject is in a comfortable state during reading.…”