RESEARCHES BASED UPON THE THEORY 



227 



is ^xlOO. It was found to be 69 per cent. The percentage of green 



sensation is - x 100. 



a 



Having obtained the percentage of white in the green the percentage 

 sensation composition of other colours in terms of luminosity can be 

 readily found 1 . Fig. 62 shows the percentage sensation curves. 



From the data obtained by these experiments the analysis of the 

 sensation- values can be carried further by calculation. Having deter- 

 mined the luminosity values of the different parts of the spectrum by 

 heterochromatic photometry (585 JJ^JL = 100) the luminosity- values of 



40 

 30 



30 

 10 



20 



25 



30 35 40 45 SO 



Scale of Prismatic Spectrum. 



55 



60 



Fig. 62. Percentage of the R. G, and B sensations in the spectrum colours in terms of 

 luminosity. Abscissae, wave-lengths of the prismatic spectrum of the arc light 

 ordinates, arbitrary scale. (Abney.) 



the R, G and V sensation can be readily obtained from their percentage- 

 values. Further it is found that the violet, which has hitherto been 

 used as a simple sensation, is made up of 72 per cent, of red sensation 

 and 28 per cent, of blue sensation. The R, G, and V values can there- 

 fore be transformed into fundamental R. G, and B sensation-values, 

 B being the fundamental blue sensation. We thus obtain the R, G, and 

 B percentage-values, and from them, by calculation, their luminosity- 

 values. 



The luminosity curves of the spectrum and of the three components 

 are shown in Fig. 63. For any wave-length the sum of the ordinates of 

 the three sensation curves is equal to the ordinate of the total luminosity 

 curve at that point. When white light, i.e., light of all wave-lengths, 

 enters the eye the effect produced on the three components will be 



1 Abney, p. 235. 



152 



