Polarization Flicker Photometer. 



371 



Fig. 



Briefness flicker 

 Color flicker 



L'. 



Critical speed relations with a difference of colour between the two 

 fields. Lower, diagrammatic; upper, experimental. Upper dashed 

 curve, limit of colour flicker region if fluctuating hue discrimination 

 fraction maintained its steady observation ratio to brightness 

 discrimination fraction. 



