DICHROMATIC VISION 



167 



The red gauging values for two protanopes (S and M) and for two 

 deuteranopes (St and N) are shown in Fig. 45. The corresponding 

 blue values are shown in Fig. 46. The abscissae are the monochromatic 

 colours of the spectrum, the ordinates the intensities in arbitrary units 



It will be noticed that Konig's blue curve extends red- wards as 

 far as 600 /A/A, whereas v. Kries and Nagel's extends only to 536 /A/A. 

 The difference shows the great importance to be attached to adaptation. 

 Every care was taken in v. Kries' experiments to make the matches 

 with good light adaptation ; no such minute precautions were taken 



70 



60 



50 



40 



30 



20 



10 



M. 



'St 



15 

 tn 

 01 



16-5 



Ol 



o 



01 



18 



10 



O) 



19- 5 



CD 

 03 



21 



CD 

 O 



Ol 



to 



24- 7 



O 

 CD 



Fig. 4G. Gauging curves for clichromats : "cokl" curves. 



as in Fig. 45. (v. Kries.) 



Same observers 



by Konig and his subjects. The latter are indeed chromatic scotopic 

 curves, in which there is some dark adaptation combined with a large 

 residual photopic condition. Another factor, however, is the much 

 greater luminosity value of red compared with that of blue (vide infra). 

 Hence the arbitrary units adopted by v. Kries do not signify equal 

 stimulus values of red and blue for the same unit-number. In their 

 gaslight dispersion spectrum one part of lithium red has about the 

 same luminosity as 8 12 parts of blue (480 /A/A.) for the deuteranope. 

 In v. Kries' units one part of red is equivalent in luminosity to about 



