Ingineria Iluminatului - Journal of Lighting Engineering - Prof. Florin ...

chroma loci, is prepared for the visual evaluation experiment. This board serves both as a background of the test colours
and a chart symbolizing the perceptual colour space as shown in Figure 3. A booth for visual experiment is constructed as
shown in Figure 4.
Colour chips on the background are illuminated uniformly by Xenon lamp (Standard illuminant D65), incandescent
lamp (Standard illuminant A), metal halide lamp MT400DL, fluorescent mercury lamp HF400X or high pressure sodium
lamp NH360 equipped on the ceiling of the booth.
Average illuminance on the board is about 1000 [lx] .
Figure 3 Board of background chart Figure 4 Booth for visual experiment
4.4 Visual estimation of colour appearance
Each observer watches colour chips placed on the
board and evaluates perceived hue, lightness and
chroma. Three under graduate students aged 22 to 24
with normal colour vision are adopted as observers for
visual experiment.
Each observer is asked to estimate subjectively the
perceived attributes, i.e., hue, chroma and lightness, of
test colour samples placed on the uniform neutral gray
background with value of 6 viewing thorough
binocular vision as shown in Figure 4 and 6.
Hue is evaluated with correspondence to red,
yellow, green, blue and purple taking perceptual
distances from these hues into consideration. Chroma is
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INGINERIA ILUMINATULUI 15-2005
estimated by way of perceptual magnitude of
chromaticness taken from neutral gray as origin.
Lightness is appraised as relative brightness compared
with black and white. The lightness of black is assumed
to be 0 and that of perfect white to be 10.
Observers express their estimated appearances by
putting the test colour chips at corresponding positions
on the chart representing appropriate hue and chroma.
According to this procedure, the observers equate
their perceived quantities with geometrical distances on
the chart of the psychological configuration colour
space.