Abstract
In evaluation of a lighting installation, the visibility under its lighting must be considered. In this report, the variations of visibility are described for experimental colored test charts lighted by different light sources.
The colored visual acuity test charts represent some series of colored Randolt's rings arranged on the colored or non-colored backgrounds.
Light sources used in these experiments are de-luxe daylight fluorescent lamps, photoflood lamps and a sodium lamp.
The following results are obtained:
(1) The value differences between the objectives and background are most influential on the visibility.
(2) The objective with a complementary color to the background gives fair visibility.
(3) In the sodium light, all colored objectives converge to be monochromatic, and the visibilities for them depend on each value difference between the objectives and the background, determinded by their reflectances for the sodium D line.
(4) By adding a continuous spectral light to the sodium light, the visibility is improved, because the color contrasts are revived slightly.
(5) When the value differences are below 0.5, the visibilities are poor.
(6) When the chroma differences are below 2, the visibilities are also poor.
