572 



BELL SYSTEM TECHNICAL JOURNAL 



sharpness which would be practically always discriminated under our ex- 

 perimental conditions, that is, a change of three or four liminal units, 

 the frequency band would have to be increased from say 2.5 megacycles 

 to about 4.5 megacycles. To effect an additional increase of the same 



CALCULATED FREQUENCY BAND IN MEGACYCLES PER SECOND 



0.5 1 2 3 4 5 6 7 8 



(O -2 



-6 



> -8 



UJ-IO 



Fig. 4- 



0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 

 RECIPROCAL OF SIDE OF SQUARE FIGURE OF CONFUSION 

 IN INVERSE MILLIRADIANS 



-Sharpness of small-sized motion pictures at a viewing distance of 30 inches. 

 The frequency band is calculated on the same basis as in Fig. 3. 



subjective amount would require that the frequency band be increased 

 from 4.5 megacycles to about 10 megacycles. The diminishing return 

 in sharpness is possibly better illustrated by the continually decreasing 

 slope of the curve in Fig. 4, in which the abscissa is proportional to the 

 square root of the frequency band, a factor which may perhaps be 

 interpreted to represent roughly the cost of electrical transmission over 

 a long system. We might infer from this curve that transmission costs 

 are likely to increase faster than image sharpness, other things being 

 equal. 



