38 Mayer — Note on the Analysis of Contrast-Colors. 



Art. IX. — Note on the Analysis of Contrast- Colors by 

 viewing, through a reflecting tube, a graded series of gray 

 discs, or rings, on colored surf aces / by Alfred M. Mayer. 



Professor Rood in his "Modern Chromatics" (N. Y., 

 1879), p. 185, et seq., describes a series of experiments he 

 made on the change which a color undergoes when darkened. 

 He gives a table of results on seventeen colors. These colors 

 were obtained as intense, saturated and brilliant as possible and 

 were painted on discs of card-board. Each of these discs was 

 placed on the rotator in combination with a disc of black, so 

 that the color could be gradually darkened by exposing more 

 and more of the black disc on the surface of the colored one. 

 He found that the effect of mixing black with some of these 

 colors was merely to darken them. The effect of mixing 

 black with others of the colors was not merely to darken these 

 colors but also to change their hues. 



On page 261 of "Modern Chromatics," Rood writes: "By 

 preparing with Indian ink a series of slips of gray paper, 

 ranging from pure white to black, an interesting series of 

 observations can be made on the conditions most favorable for 

 the production of strong contrast-colors. The strongest con- 

 trast will be produced in the case of red, orange and yellow, 

 when the gray slip is a little darker than the color on which it 

 is placed, the reverse being true of green, blue, violet and 

 purple ; in every case the contrast is weaker if the gray slip is 

 much lighter or much darker than the ground." 



The particular gray which gives the strongest contrast-color 

 effect on a given colored ground can only be determined 

 experimentally by observing a graded series of gray surfaces 

 placed on the colored ground. In this manner 1 obtained the 

 grays used in " Studies of the Phenomena of Simultaneous 

 Contrast-color," etc., this Journal, July, 1893. These grays, 

 however, were not selected by the unaided eye but by viewing 

 the gray surfaces through my reflecting tube, which doubles 

 the saturation and brilliancy of the contrast-color.* This 

 increase in the saturation and brilliancy of the contrast-color 

 renders the selection of the proper gray easy and definite. 



The fact that the mixing of black optically with a color 

 either merely darkens it, or changes its hue at the same time 

 it darkens it, taken in connection with the fact that different 

 depths of gray are required to give the maximum contrast- 

 color effect on different colored surfaces, seems to me to offer, 



* This Journal, July, 1893, p. 7 et seq. 



