Comparative Effects of Area and Luminance on Color

The present study evolved from a practical interest in the color differences that may be expected in enlarged colored photographs as compared to smaller originals, differences which are found even when pertinent photographic factors have been controlled. A previous study by the present investigator was undertaken to measure such differences.l The results suggested that color may be dependent upon area in much the same way that it is upon luminance.2 In particular the data showed saturation changes (as area was varied) that were similar in trend to those reported elsewhere when luminance was varied. Purdy, for example, has shown that, by increasing luminance up to an optimal point, colors increase in saturation and that at progressively higher luminances they decrease.3 The study of area by the present investigator showed a similar increase and reversal for saturation as the visual angle of test-colors was increased up to and beyond a certain magnitude. It became of some interest, therefore, to investigate directly this apparent similarity between stimulus-area and luminance in producing color changes.4 The specific problem of the present study was to determine the relative color changes in surface colors for variations in their visual angle and in their luminance. The experiment was of limited scope, involving two levels of each of these factors. Although the two levels of area and luminance covered only ranges in which a progressive increase in saturation has been reported, they make possible a direct comparison of the results obtained in a given experimental setting.5