34 AMES, PROCTOR AND AMES. 



SUMMARY. 



The above facts show the marked effect that variations in sensitivity 

 of the retina have on the nature of our retinal picture. 



The slightly brighter warmer centers in some of Corot's pictures 

 suggest the effect produced by the yellow spot. But besides his work 

 the only evidence that has been found that the above described effects 

 have been made use of by artists is in their very common practice of 

 rendering shadows in out-of-door scenes much bluer than the}' appear 

 when one looks directly at them. As far as is known this has not been 

 limited to the outer parts of their pictures. The blue appearance of 

 shadows which are imaged on the side of the retina are, however, very 

 easily seen, and as this effect holds true over the greater part of the field 

 of vision it was probably found that pictures look better with blue 

 shadows all over them than without any blue shadows at all. 



As has been stated our knowledge of the sensitivity of the retina is 

 very limited. We already know, however, that our capacity to dis- 

 tinguish detail away from the center of focus is largely due to the 

 structure of the retina. It is probable that a further knowledge would 

 give suggestions as to the laws which control the difference of local 

 values of which we are conscious on the different parts of the retina. 



There are also of course other effects such as contrast, simultaneous 

 and successive, and after images which must have a marked influence 

 on our retinal picture. Their use in pictures raises the thought of the 

 possibility of suggesting eye motion. 



Chapter VI. 

 BIXOCULAR VISION. 



The fundamental idea in undertaking the research work which is 

 the basis of this article was that pictorial art should be similar to our 

 mental visual images, and, since our mental visual images are probably 

 similar to our retinal pictures, valuable suggestions could be obtained 

 from a knowledge of the characteristics of our retinal picture. Our 

 mental visual impression, however, is not derived from a single retinal 

 picture but from two, as we normally look with two eyes. 



The whole subject of binocular vision is too long and complicated to 

 be considered here. It was believed, however, that some of the char- 

 acteristics of binocular vision under particular conditions could be 

 reproduced in a single picture such as a photograph or painting. 



