VISION AND THE TECHNIQUE OF ART. 37 



All oblique objects are distorted and changed in shape varying in 

 amount with their obliquity. This distortion is shown in the bowing 

 out in their central portions of straight lines which do not pass through 

 the center of interest and a reduction in size of oblique objects. 



And finally the color of the picture in its outer parts is bluer than at 

 its center. 



In our ordinary habit of vision, when looking at a scene, we focus on 

 some particular part or object in it due to its special interest or beauty 

 to us; we hold that focus for a moment or two and then look at 

 another center of interest or another or look away entirely. With 

 each fixation of the eye a retinal picture of the kind just described is 

 formed. We therefore receive on our retinas a series of such pictures. 



MENTAL VISUAL IMAGES. 



The question arises : What is the nature of the mental visual images 

 which we have of actuality? Without doubt, our brain receives a 

 series of impressions similar in character to our retinal pictures. But 

 how are those impressions registered in our consciousness and memory. 

 There are two general possibilities. One that our visual memory 

 consists of a series of pictures similar in nature to our retinal pictures. 

 The other that, by some mental process, these serial impressions are 

 combined and form a memory impression similar to actuality as we 

 know it exists intellectually, i.e., with the detail all over the picture 

 sharp and clear and with no colored edges or distortion. 



Although there is no known psychological work on the analysis of 

 mental visual images to substantiate the conclusion, what evidence 

 there is indicates that our mental visual images consist of a series of 

 images similar to our retinal pictures. This was the opinion of the 

 well known psychologist, Dr. J. W. Baird, who mentioned as a reason 

 for such belief the relatively definite character of the center and 

 nebulous character of the outer parts of our mental visual images both 

 when we are awake and when we are dreaming. Such a view is further 

 substantiated by the fact that the indefiniteness in those parts of a 

 scene that are not at the focus point and other characteristics of our 

 retinal picture give a sense of depth and relief. A sacrifice of these 

 characteristics would mean a sacrifice of effect of depth in our mental 

 visual images which would seem most improbable. 



Furthermore the existence of a mental visual image of a scene similar 

 in detail to the scene itself could only be based on a visual knowledge 

 of all the detail in the scene. This could only be acquired by passing 



