EXAMINATION OF THE EFFECTS OF LEVEL OF ILLUMINATION, STROKE-WIDTH, VISUAL ANGLE AND CONTRAST ON LEGIBILITY OF NUMERALS SHOWS THAT SOME FONTS TESTED ARE SIGNIFICANTLY BETTER THAN OTHERS. THERE IS AN OPTIMUM LUMINANCE LEVEL (OF ABOUT 34.3 CD/SQ.M) FOR LEGIBILITY OF WHITE LETTERS ON A BLACK BACKGROUND. WHITE LETTERS ON BLACK BACKGROUND ARE SIGNIFICANTLY MORE LEGIBLE THAN BLACK NUMERALS ON A WHITE BACKGROUND. OPTIMUM LEGIBILITY IS OBTAINED WHEN STROKE-WIDTH/HEIGHT RATIOS ARE LESS THAN 1/6 FOR BLACK NUMERALS AND ABOUT 1/12 FOR WHITE NUMERALS. A SET OF NUMERALS WAS SELECTED FROM ALL THOSE TESTED WHICH IS SIGNIFICANTLY BETTER THAN ANY OF THE STANDARD SETS, PARTICULARLY FOR BLACK NUMERALS ON A WHITE BACKGROUND. (A). FOR THE COVERING ABSTRACT OF THE CONFERENCE PROCEEDINGS SEE IRRD ABSTRACT NO. 226354.
Samenvatting