How to Make Large Screen Displays Legible

Abstract

Four major display variables, luminance adaptation level, symbol contrast ratio, symbol visual size and off-axis viewing angle, were related, in a rotatable central composite design, to an observer's ability to identify symbols shown on a large screen display (LSD). The results show the nature and significance of all main effects as well as delineate the important interactions among these variables. The results can be used as an LSD design and evaluation tool permitting tradeoffs to be made among the important features of display equipment, projection screens and viewing facilities.

Human Engineering Data Base for Design and Selection of Cathode Ray Tube and Other Display Systems

“…The relative importance of display parameters and the availability of knowledge about these parameters are shown in Table 3 (taken from Shurtleff, 1980). Admittedly, there is a certain amount of subjectivity in all these judgments.…”

“…One complication is that the acceptable minimum ratio depends on a number of factors: absolute luminance levels, symbol size, and symbol blur. Shurtleff (1980) …”

“…For low values of absolute luminance (.01 to .1 fL), a minimum visual size of 20 minutes of arc is recommended by Shurtleff (1980); for intermediate values of absolute luminance (10 to 50 fL), a minimum visual size of 10 minutes of arc is recommended. A stroke-width-to-height ratio of 1:5 and a symbol width of 15 percent of symbol height are recommended for displays.…”

“…No meaningful loss in rate of identification (symbols per second) was observed. Shurtleff (1980) recommends that CRT beam defocussing should be kept to a minimum, although slight defocussing, which increases stroke widths up to 20 percent, can be tolerated with little decrease in identification accuracy.…”

“…For digital TV, in which symbols are constructed by a symbol gener tor rather than from input from a TV camerei, bandwidth requirements can be calculated by use of the following formula (Shurtleff, 1980):…”