According to the present standard procedure to estimate the light fastness of printed or dyed materials, they are exposed to light together with standard color, and the change of color is compared by eyesight.
Though this procedure is advantageous, being its simplicity, it is insufficient to express the light fastness accurately and quantitatively or to estimate the degree of fading.
For the purpose of getting numerical light-fastness, after defined the vector of fading in the theory of color difference, we tried to take a comparison of the data from our tentative method with those of JIS L-1044 (1959).
Consequently we found our methd have a satisfactory correspondence with of the JIS and good results for the color measuring.
