104 Mr. H. E. Ives on Hue Difference 



the blue component necessary to bring it up to equal 

 luminosity with the others, so that the third member of (5) 

 practically has the whole say in any distance determination, 

 simplifies the evaluation of colour differences in hue difference 

 units, since such hue discrimination data as we have can 

 be most easily grasped when plotted in the equal sensation 

 triangle. 



^ In figs. 2 a, b, c, and d are shown (dotted lines) the 

 •distances of the various parts of the spectrum respectively 



Fig. 2 a. 



Dotted lines : Colour Triangle distances. 



Dashed lines : Corrected distances, taking into account variable size of 



equal hue distances at equal luminosity mixture points. 

 Ftdl lines : Speeds as calculated for dashed line data and relationship 



plotted in fig. 1. 

 Dots : Experimentally found speeds, in arbitrary units. 



2 a. — Spectrum against red light. 



2 b. — Spectrum against blue light. 



2 c. — Spectrum against yellow-white (tungsten lamp). 



2 d. — Spectrum against white (5000° black body). 



