- Email: [email protected]
Measurements of brightness-difference perception and hue-difference perception by steady and intermittent vision
542
U.G.I.
COMPANY NOTES.
[J.F.I.
brightness of the two fields. The results are in complete agreement with the previously developed theory, accurate confirmation of which had not been found possible with the ordinary type of flicker photometer. MEASUREMENTS OF BRIGHTNESS-DIFFERENCE PERCEPT I O N A N D H U E - D I F F E R E N C E P E R C E P T I O N BY S T E A D Y AND INTERMITTENT VISION. By Herbert E. Ives.
IN the theory of the flicker photometer as developed by the writer and Mr. Kingsbury * there figure two fractions, the brightness discrimination fraction, and the hue discrimination fraction. The former conditions the critical speed when two unequal fields of the same color are alternated, the latter when two equally bright fields of different color are alternated. These fractions are the least fractional parts appreciable by the ultimate receiving apparatus of the eye (presumably the brain), for successive impressions over the same path, and are neither susceptible of direct measurement. They can, however, be solved for from the equations of the theory, provided experimental constants can be obtained for stinmli following the simple sine curve variation of intensity which alone is susceptible of mathematical treatment. The new polarization flicker photometer (see previous note) provides just such data, and has made possible the determination of the numerical values of these constants, and, what is more important, their relative values as compared to the same quantities for steady observation. The value of the ultimate brightness discrimination fraction for intermittent light is found to be of the order of magnitude of one-fiftieth of one per cent. The hue discrimination fraction is of course dependent on the size of the color difference worked with. A complete determination of brightness and hue discrimination fractions, both steady and intermittent, for a certain large color difference, shows that the ratio of hue fraction to brightness fraction is about ten times larger for intermittent than for steady vision. Herein lies the reason for the success of the flicker photometer, for if these fractions maintained their steady relationship, the flicker photometer would have to be run at such speed, in order to eliminate color flicker, that no sensibility would be left. 1,, Theory of the Flicker Photometer." Ives and Kingsbury, Philosophical Magazine, November, I915, p. 7o8, April, I916, p. 29o.
U.G.I.
COMPANY NOTES.
[J.F.I.
brightness of the two fields. The results are in complete agreement with the previously developed theory, accurate confirmation of which had not been found possible with the ordinary type of flicker photometer. MEASUREMENTS OF BRIGHTNESS-DIFFERENCE PERCEPT I O N A N D H U E - D I F F E R E N C E P E R C E P T I O N BY S T E A D Y AND INTERMITTENT VISION. By Herbert E. Ives.
IN the theory of the flicker photometer as developed by the writer and Mr. Kingsbury * there figure two fractions, the brightness discrimination fraction, and the hue discrimination fraction. The former conditions the critical speed when two unequal fields of the same color are alternated, the latter when two equally bright fields of different color are alternated. These fractions are the least fractional parts appreciable by the ultimate receiving apparatus of the eye (presumably the brain), for successive impressions over the same path, and are neither susceptible of direct measurement. They can, however, be solved for from the equations of the theory, provided experimental constants can be obtained for stinmli following the simple sine curve variation of intensity which alone is susceptible of mathematical treatment. The new polarization flicker photometer (see previous note) provides just such data, and has made possible the determination of the numerical values of these constants, and, what is more important, their relative values as compared to the same quantities for steady observation. The value of the ultimate brightness discrimination fraction for intermittent light is found to be of the order of magnitude of one-fiftieth of one per cent. The hue discrimination fraction is of course dependent on the size of the color difference worked with. A complete determination of brightness and hue discrimination fractions, both steady and intermittent, for a certain large color difference, shows that the ratio of hue fraction to brightness fraction is about ten times larger for intermittent than for steady vision. Herein lies the reason for the success of the flicker photometer, for if these fractions maintained their steady relationship, the flicker photometer would have to be run at such speed, in order to eliminate color flicker, that no sensibility would be left. 1,, Theory of the Flicker Photometer." Ives and Kingsbury, Philosophical Magazine, November, I915, p. 7o8, April, I916, p. 29o.