SUBJECTIVE SHARPNESS OF IMAGES 



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that images of present television grade are well within a region of 

 diminishing return with respect to resolution, a region, however, whose 

 ultimate boundary is still well removed. (We estimate that the sharp- 

 est image our motion picture machine could project would be repre- 



20 40 60 80 100 120 140 160 180 



THOUSANDS OF FIGURES OF CONFUSION IN THE CONVENTIONAL FIELD OF VIEW 



Fig. 1 — Sharpness of small-sized motion pictures as a function of resolution. The 

 conventional field of view is a rectangle whose height is 1/4 the viewing distance and 

 whose width is 4/3 the height. Reference sharpness is approximately that of a 240- 

 line, 24 frame per second, 806 kilocycle television image. Curve based on 1,080 

 observations at a viewing distance of 30 inches. 



sented in Fig. 1 by a point in the neighborhood of + 18 units.) It 

 must be remembered that the curve represents judgments made by 

 trained observers under optimum conditions for distinguishing small 

 differences, and that a change as small as one liminal unit, under the 

 conditions of ordinary television viewing, would probably be largely 

 unnoticed. 



A better understanding of the meaning of this curve relating sharp- 

 ness to resolution may be had by examining the experiment in detail. 

 An individual observation was made when one of the observers, watch- 

 ing the projected image, caused the projection lens to be moved from 

 a reference position to a neighboring one and reported which position 

 he judged to yield the sharper image. The motion picture scene was 

 a close-up of a fashion model turning slowly against a plain neutral 



