SUBJECTIVE SHARPNESS OF IMAGES 585 



The Observers 



The observers were almost all Laboratories engineers associated with 

 television research and transmission problems. The average observer 

 devoted about one hour to the experiment on unequal horizontal and 

 vertical resolutions, and about three hours (in two sessions) to the 

 experiment on small differences in resolution. Each observer was 

 carefully instructed with regard to the purpose and the mechanism of 

 the experiments, and was allowed to examine trial pictures to see 

 clearly the effects of changing the shape and size of the figure of 

 confusion. 



Motion Picture Film 



Standard 35 mm. black-and-white sound film on safety base. The 

 area projected onto the screen was 0.600 inch high by 0.633 inch wide. 



For the experiment on unequal horizontal and vertical resolutions, 

 five different scenes were used. Sample frames from them are shown 

 in Fig. 10. For the experiment on small resolution differences, Scene 3 

 was selected as the most suitable on the basis of photographic excellence 

 and picture content, and this alone was used. Each of the scenes was 

 about one quarter of a minute in length, and was shown repeatedly. 

 Brief descriptions follow: 



Scene 1: A country-side landscape, with trees and fields. A center 

 of interest is the tall steeple of a white church on the distant hillside. 

 A concrete highway flanked by a white fence carries cars into and out 

 of the picture. There is no fast motion. 



Scene 2: A full-length view of a girl modeling an evening dress 

 moving slowly against a dark, fluted backdrop. A large vase of flowers 

 is a secondary center of interest. 



Scene 3: A close-up view of a girl modeling a hat, turning slowly 

 against a plain, neutral background. 



Scene 4: A street scene of an Indian parade, with a background of 

 store windows and signs. The parade moves rather rapidly, and there 

 is some motion among the by-standers. 



Scene 5 : A closer view of some of the Indians in the parade. There 

 is much fine detail in the costumes, and the motion is rapid. 



References 



1. M. Luckiesh and Frank K. Moss, "The Dependency of Visual Acuity Upon 



Stimulus-Distance," Jour. Opt. Soc. Amer., 23, 25 (Jan. 1933). 



2. J. P. Guilford, "Psychometric Methods," McGraw-Hill, New York, 1936. 



3. R. D. Kell, A. V. Bedford and M. A. Trainer, "An Experimental Television 



System," Proc. I.R.E., 22, 1246 (Nov. 1934). 



