PHYSIOLOGY OF COLOR VISION 459 



changes in hue and saturation which they would have suffered by con- 

 trast with red. Thus orange will stand nearer the center and somewhat 

 nearer yellow, whereas green-blue will merely be removed farther from 

 the center, which means that orange will become less saturated and 

 yellower, whereas green-blue will increase in saturation but be unaltered 

 in hue. 



In general we may say that the effect produced by contrasting two 

 colors is to move them farther apart on the chromatic circle, thus 

 causing mainly a change in hue in the case of colors that stand near 

 one another, but making a change in saturation in those which are far 

 apart. 



In order that the contrast effects may be taken full advantage of, 

 certain conditions must be fulfilled. The most important of these are 

 as follows: (1) The complementary tint which gray assumes is most 

 vivid when it is somewhat darker {i. e., of less brightness, see p. 460) 

 than the hue against which it is apposed, in the case of the warm colors 

 (the reds, oranges and yellows), and when it is lighter in the case of the 

 cold colors (the greens and blues). The dividing line between the warm 

 and cold colors may be taken as that joining the complementaries, 

 5'ellow-green and violet. (2) When a color of low saturation {%. e., 

 nearly a gray) is apposed to one of high saturation and of comple- 

 mentary hue, the former will become more saturated, and conversely, if 

 two colors which are identical in hue but of unequal saturation be ap- 

 posed, the paler one may appear gray. When they are not comple- 

 mentary, the hue which undergoes the greater change is that which is 

 the paler. (3) The greatest effects are produced when the color field, 

 whose hue it is desired to alter, is much smaller in extent than that of 

 its complementary and when it is completely surrounded by the latter. 

 By placing a thick black line betw^een the areas the complementary 

 effects may be suppressed. Thus, the complementary hue which a piece 

 of gray paper placed on a colored field assumes when it is viewed 

 through tissue paper becomes much less evident if a thick black line be 

 drawn on the tissue paper at the edge of the gray. When the color areas 

 are large it is at the edge only that the complementary influence 

 is noticeable. On the other hand when a colored area is very small 

 it undergoes no complementary change, but merely blends with the 

 neighboring color. (4) To obtain full advantage of color apposition the 

 colored patterns should be very simple and of similar texture and their 

 surfaces should be broken up by detail to the least possible degree. (5) 

 The most marked complementary effects are obtained when the opposing 

 hues are of equal brightness. 



When we attempt to employ the chromatic circle for another purpose, 

 namely for determining what will be pleasing and what displeasing 

 color combinations, we find that its use is somewhat limited. This is 

 because a psychological influence enters into our judgment in such cases. 



