118 ON THE RELATION OF OPTICS TO PAINTING. 



however, works for the most part with the latter. He 

 produces most of his tints by mixture ; each mixed 

 pigment is, however, greyer and duller than the pure 

 colour of which it is mixed, and even the few pig- 

 ments of a highly saturated shade, which oil-painting 

 can employ, are comparatively dark. The pigments 

 employed in water-colours and coloured chalks are 

 again comparatively white. Hence such bright con- 

 trasts, as are observed in strongly coloured and strongly 

 lighted objects in nature, cannot be expected from 

 their representation in the picture. If, therefore, 

 with the pigments at his command, the artist wishes 

 to reproduce the impression which objects give, as 

 strikingly as possible, he must paint the contrasts 

 which they produce. If the colours on the picture 

 are as brilliant and luminous as in the actual objects, 

 the contrasts in the former case would produce them- 

 selves as spontaneously as in the latter. Here, also, 

 subjective phenomena of the eye must be objectively 

 introduced into the picture, because the scale of colour 

 and of brightness is different upon the latter. 



With a little attention you will see that painters 

 and draughtsmen generally make a plain uniformly 

 lighted surface brighter, where it is close to a dark 

 object, and darker, where it is near a light object. 

 You will find that uniform grey surfaces are given 

 a yellowish tint at the edge where there is a back- 



