The experimental design called for a pair of identical “art gallery” settings to be viewed
sequentially; i.e., not simultaneously. Two adjacent partitioned offices measuring 8 feet 6
inches by 6 feet 9 inches by 7 feet high were lined with white “Foamcore”, and three pairs of
identical prints of artworks were presented in these simulated “art gallery” settings. Figure 5
shows one of the galleries. The artworks selected were (refer to the paintings).
The comparison condition was lit by an MR lamp that was preset by the experimenter to an
illuminance of 50 lux. The test condition was lit alternately by a MR lamp identical to the one
in the comparison condition, or by the 3-band source adjusted to have CCT and chromaticity
matched to the comparison source. The arrangement of the light sources in the test room,
including the sensors connected to the feedback device, is shown in Figure 9.
Each subject was taken to the comparison situation, where one of the artworks was on display
at the preset illuminance. They were instructed to suppose that this was an art gallery, and that
they had come to see this picture. Then they were taken to the test situation where the
identical artwork was on display, and they were told to adjust the control “to match the
appearance of this situation as closely as possible to the appearance of the previous situation”.
Subjects could return to the comparison situation as often as they wished, but could not view
the two situations simultaneously. When a setting had been made, the experimenter recorded
the control reading and asked the subject whether they could see any differences between the
two situations, using five categories of difference:
- Brightness
- Clarity
- Acceptability of overall color appearance
- Brightness or colorfulness of individual colors
- Naturalness of individual colors
A seven-point scale of difference was used to describe the magnitude of the difference of appearance of the test situation relative to the comparison situation: +3 Much more; +2 More; +1 Slightly more; 0 No difference; -1 Slightly less; -2 Less; -3 much less.
For each phase of the experiment, subjects made six settings, one for each of the two light
sources illuminating each of the three artworks. The order of presentations was
randomized. The light source CCT was approximately 2850K for the first phase, and
subjects returned to repeat the procedure for the second phase, for which the CCT was
approximately 4200K. Light source data are given in Table 1.
- Table 1.
- Data for the two light source types at low and intermediate correlated color
temperatures in the test situation.
|
Low CCT |
Intermediate CCT |
|
MR |
3-band |
MR |
3-band |
Correlated color
temperature (K) |
2857 |
2856 |
4185 |
4197 |
Chromaticities:
x
y |
0.4492
0.4107 |
0.4487
0.4098 |
0.3766
0.3885 |
0.3761
0.3884 |
Radiant
Luminous
Efficacy
(lm/Wr) |
224 |
380 |
252 |
367 |