548 VISION 



see a gray ring, corresponding to the black and white strip, on a faintly 

 colored whitish ground. But instead of looking gray, the ring takes the 

 complementary color of the ground. 



Standing in the moonlight and the gaslight at the same time, a person 

 casts two shadows one from the moonlight, the other from the gaslight. 

 The ground, being illuminated by both the moon and the yellow-red light 

 of the gas flame, takes the color of the latter. The shadow from the moon- 

 light is also yellow red, for it is likewise illuminated by the gaslight. The 

 other shadow which is illuminated by the moonlight ought to be gray, but 

 is not. It has instead a bluish color i. e., the complementary color of the 

 ground. 



Simultaneous contrast therefore means that an object without color, in 

 the neighborhood of a colored one, takes on a tint which is the complement 



of the color in the object beside which 

 it is placed. In the same way a bright 

 object in the neighborhood of a dark one 

 looks brighter than it really is. 



We are all the time meeting with con- 

 trast phenomena which influence in many 

 ways the impression we get of color com- 

 positions. If, for example, a black design 

 be printed on a red material, the design 

 does not appear black, but because of the 

 contrast greenish blue. In order to make 

 the design actually appear black, it is 

 necessary to mix a little of the ground 

 color with the black i. e., in this case 

 the design must be printed in a very dark 

 FIG. 239. After Helmholtz. red. The greenish blue produced by con- 



trast then mixes with the red of the de- 

 sign, giving a faint white; hence the design no longer appears greenish blue, 

 but black (Chevreul). 



If on the other hand the design and ground work are complementary colors, 

 they intensify each other. A yellow design on a blue material stands out much 

 more prominently than it would on any other color; and the same is true of 

 course of black and white. Phenomena of this kind are of no little importance 

 in securing sharpness of vision. 



It is evident that these contrast phenomena are entirely of subjective origin 

 and cannot be caused by any objective influence of the one color on another. 



According to Helmholtz it is all a matter of judgment. We are accus- 

 tomed to subtract from all colored surfaces without distinction the light by 

 which they are illuminated, so far as that is in the region of their own color, 

 in order to find the body color itself. If gaslight and moonlight fall on the 

 same spot, the illumination of the ground is a light yellow red. Now this 

 yellow red we abstract not only from the color of the ground, but also from 

 that of the shadow, on which no gaslight falls; hence it looks blue when it 

 is really white. 



Hering on the basis of a great variety of experiments makes different 

 objections to this view, and in many cases at least has succeeded in showing 



