An Appraisment of the Color Rendering Properties of Fluorescent Lamps

Abstract

For all the plausible attempts of the investigators in evaluating the color rendering properties of fluorescent lamps on the bases of colorimetric specifications, it is as yet undeniable that they are to be found mistaken in neglecting the variable of luminance, and apparent luminance changes of objects by light sources, we believe, are very important factors determining the pratical acceptability of the light sources. So the authors propose a new method of appraising these properties dealing with the distances between color points of defined 20 color papers under the sample light and of those under the standard light in a 3-dimentional metric color space. Munsell renotation system is adopted as the metric color space, and the interrelation of the steps of the three attributs is assumed to be 0.1V=0.4C≠1H (at C=6). In one of the three methods adopted to calculate the color distances, chromatisity differences of the light sources are compensable by appropriate parallel displacement of the color solid ; and it is concluded that this method gives the most reasonable measure of the color rendering properties of lamps for each color of objects.It is apparent from the results that the considerable color distortion occurs in colors in the neighbourhood of red under the standard type lamps while the defects are markedly reduced by the de luxe type lamps and a mixed light of fluorescent lamps and incandescent lamps. The arithmetical mean of these distances of color displacements, which gives a single merit figure of the over all color rendition by a lamp, leads to the general conclusion that the de luxe white fluorescent lamp is superior not only to the standard white fluorescent lamp but also to the special de luxe white fluorescent lamp which applies a kind of deep red phosphor.