56 



HOW WE SEE 



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o 



-3 



LOGARITHM OF STANDARD LUMINANCE (mL.) 

 Fig.' 46. Luminance of a test area judged to be half as bright as another test area. (After Hanes, 33) 



y 



.10 .20 .30 40 50 .60 



Fig. 47. Distances from the center of any ellipse to a boundary represent chromaticity differences 

 which are equally noticeable. The ellipses have been magnified ten times. (After MacAdam, 63) 



