VISION AND THE TECHNIQUE OF ART. 39 



objects are depicted, they do not reproduce the positioning of objects 

 situated at different distances. This is impossible because a picture is, 

 of necessity, on a flat surface where everything depicted must be the 

 same distance from the observer, whereas nature exists in tri-dimen- 

 sional space. 15 Due to this fact, the picture as a whole can never give 

 the same effect to one looking at it as one gets from looking at nature. 

 For in looking at one part of a natural scene, objects at all other dis- 

 tances take on characteristic appearances due to their different dis- 

 tances. In a picture where they are all reduced to one plane this is 

 not true. 



The second way in which the depicting of nature can be attempted 

 is, instead of trying to reproduce actuality itself, to attempt to repro- 

 duce the impression that nature makes on the human consciousness, 

 i.e., to reproduce mental visual images. The general characteristics 

 of our mental visual images are, as it is believed it has been shown, 

 similar to those of the retinal pictures. 



Such depicting of nature can be approximated photographically by 

 means of a lens which produces the same characteristic imaging as the 

 lens system of the eye, and a plate whose sensitivity over its various 

 parts is similar to that of the retina. It can be approximated in paint- 

 ings and drawings if the artist keeps focused on whatever he picks out 

 as the center of interest and depicts everything else as it appears to 

 him while keeping his eye focused on that point. Artists who have 

 very clear and lasting mental visual images closely approximate it by 

 copying those images directly without regard to actuality. 



As the retinal picture lies on a surface and as the canvas or paper 

 on which it is depicted is also a plane surface, there does not seem to 

 be the same fundamental limitations in reproducing it that exists in 

 attempting to reproduce tri-dimensional actuality. In reproducing 

 the subjective binocular impression in a single picture there do exist, 

 however, the limitations which arise from the impossibility of repro- 

 ducing those parts of the impression which we get from eye movement 

 and motor impulses. 



For all artistic purposes, it is believed that the attempt should be to 

 reproduce not the actuality but the impression which it makes on us. 

 Three general facts may be given in support of this. 



First, the use by so many of the great painters of characteristics of 

 the retinal picture which is the strongest evidence of the artistic value 



!5 Stereoscopic photographs do reproduce the effect of the third dimension. 

 They are not however satisfactory from an artistic point of view, and as we are 

 dealing only with single pictures will not be considered here. 



