ON THE RELATION OF OPTICS TO PAINTING. 105 



judgment as to the lighter or darker colour of the 

 bodies we see. Now this ratio can be imitated by the 

 painter without restraint, and in conformity with na- 

 ture, to evoke in us the same conception as to the 

 nature of the bodies seen. A truthful imitation in this 

 respect would be attained within the limits in which 

 Fechner's law holds, if the artist reproduced the fully 

 lighted parts of the objects which he has to represent 

 with pigments, which, with the same light, were equal 

 to the colours to be represented. This is approximately 

 the case. On the whole, the painter chooses coloured 

 pigments which almost exactly reproduce the colours of 

 the bodies represented, especially for objects of no great 

 depth, such as portraits, and which are only darker in 

 the shaded parts. Children begin to paint on this 

 principle; they imitate one colour by another; and y 

 in like manner also, nations in which painting has- 

 remained in a childish stage. Perfect artistic painting 

 is only reached when we have succeeded in imitating 

 the action of light upon the eye, and not merely the 

 pigments; and only when we look at the object of 

 pictorial representation from this point of view, will it 

 be possible to understand the variations from nature 

 which artists have to make in the choice of their scale 

 of colour and of shade. 



These are, in the first case, due to the circumstance 

 that Fechner's law only holds for mean degrees of 



