Lightness and Brightness and Other Confusions
Lightness and Brightness and Other Confusions
Lightness and Brightness and Other Confusions
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P<br />
Y<br />
ment with coloured Munsell papers. 4 A 40-step hue set of constant lightness<br />
<strong>and</strong> chroma was used. The Munsell chips are approximately perceptually<br />
equispaced, so each chip is 1/40 of the hue circle. Observers adapted to a<br />
st<strong>and</strong>ard illuminant <strong>and</strong> viewed the chips against a light grey background.<br />
The figure shows the range of mean unique hue choices. Each observer performed<br />
the experiment three times. This enabled a comparison of variability<br />
within <strong>and</strong> between observers.<br />
90<br />
10 P<br />
95<br />
2,5 RP<br />
5 RP<br />
7,5 RP<br />
RP<br />
100<br />
10 RP<br />
2,5 R<br />
5<br />
5 R<br />
R<br />
7,5 R<br />
10<br />
10 R<br />
2,5 YR<br />
YR<br />
15<br />
5 YR<br />
7,5 YR<br />
10 YR<br />
20<br />
2,5 Y<br />
7,5 P<br />
85<br />
25<br />
5 P<br />
5 Y<br />
80<br />
10 PB<br />
2,5 P<br />
7,5 PB<br />
N<br />
7,5 Y<br />
2,5 GY<br />
10 Y<br />
30<br />
PB<br />
GY<br />
5 PB<br />
75<br />
5 GY<br />
35<br />
2,5 PB<br />
7,5 GY<br />
10 B<br />
70<br />
7,5 B<br />
5 B<br />
65<br />
B<br />
2,5 B<br />
10 BG<br />
60<br />
7,5 BG<br />
BG<br />
5 BG<br />
55<br />
2,5 BG<br />
G<br />
10 G<br />
50<br />
7,5 G<br />
5 G<br />
45<br />
2,5 G<br />
10 GY<br />
40<br />
Figure 1. Conceptual hue circle diagram of the Munsell system with the<br />
ranges of samples (marked with arrows) selected to represent the four<br />
unique hues of the Hinks et al. experiment.<br />
Only about 15% of the variability is intra-observer. The sum of the ranges in<br />
the diagram showing individual unique hue sample choices is 57.5% of the<br />
total. Observers can vary significantly in their individual “signatures” of<br />
unique hue choices. This suggests that there may not be a simple mechanism<br />
guiding unique hue stimulus choices. Perhaps past visual experiences are<br />
4<br />
Hinks, D., L. Cardenas, R. Shamey, R. G. Kuehni. (2007) Unique Hue Stimulus Selection<br />
Using Munsell Color Chips. Journal of the Optical Society of America A 26, 3371-<br />
3378.<br />
13