424 



FLICKER WITH MOVING PICTURES 



[CH. XI 



00 I 234 



Logarithm of ILLumination 



FIG. 234. THE RELATION BETWEEN THE ILLUMINATION OF THE SCREEN 



AND THE NUMBER OF FLASHES PER SECOND AT WHICH FLICKER JUST 



DISAPPEARS. 



If the flashes are more frequent than indicated by the curve for a given 

 illumination there will be no flicker, but if less frequent, flicker will be seen. 



The solid line represents the observation of T. C. Porter and the dotted line 

 represents some rough observations made by the authors. 



