4. Result
4.4 Effect of adaptation condition on Color appearance estimation
In this chapter, the analysis is focused on the change in color appearance according to the adaptation conditions. There were two lightings: low luminance lighting with an adapting field of 56.9 cd/m2 luminance and high luminance lighting with an adapting field of 273.91 cd/m2 luminance. In the case of a single lighting condition, it is when adaptation to low luminance or high luminance lighting alone is done. In the case of a mixed adaptation, it refers to the adaptation in a situation where both lights are on. Under the two conditions of adaptation, there were two luminance levels, low and high luminance, so the color appearance under the two luminance conditions were analyzed separately.
The same test set of colors are estimated in both single and mixed lighting adaptation conditions.
Therefore, it is possible to investigate changes according to the adaptation conditions for the same color.
Hue, brightness, and colorfulness of the test colors were estimated repeatedly in experiment sessions.
The color appearance is compared according to the adaptation, so the estimation of the color appearance data of the single adaptation at low luminance and the mixed adaptation at low luminance are compared. The estimation of single adaptation at high luminance and estimation of mixed adaptation at high luminance were compared.
The paired t-test was used for statistical analysis of the data. For each test color, it is judged whether the responses in the single adaptation and the responses in the mixed adaptation are significantly different (p<0.05).
4.4.1 Effect of adaptation condition on Hue estimation
The hue of set A colors at low luminance and set B colors at high luminance were estimated. In Figure 24, Figure 25, the horizontal axis represents the average response of the hue estimation for the test color under single adaptation. The vertical axis represents the average response of the hue estimation for test colors set in the mixed adaptation. Each data point represents one test color. Colors of set A and set B were estimated for hue in single adaptation and mixed adaptation.
In Figure 24 and Figure 25, data points are close to the 45° line, which means that the test color showed no difference in response under the two adaptations. Test colors that showed significantly different responses in the two adaptations are indicated by red squares.
In low luminance, one test color of GB was observed to be bluish in mixed lighting (Figure 24). At high luminance, the two test colors of the YG group were observed to be more greenish, and one test color of the GB group was observed to be more bluish in the mixed lighting adaptation (Figure 25).
Figure 24 Hue estimation in single adaptation and mixed adaptation under Low Luminance Lighting
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Response in Mixed Adaptation (Low luminance)
Response in Single Adaptation (Low luminance)
Figure 25 Hue estimation in single adaptation and mixed adaptation under High Luminance Lighting
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Response in Mixed Adaptation (Highluminance)
Response in Single Adaptation (High luminance)
4.4.2 Effect of adaptation condition on brightness estimation
This chapter shows the change of brightness appearance according to the conditions of adaptation.
The brightness of colors in set C at low luminance and set D colors at high luminance were estimated.
In Figure 26, Figure 27, the horizontal axis represents the average response of the brightness estimation for the test color under a single lighting adaptation. The vertical axis represents the average response of the brightness estimation for the test colors of set C and D in the mixed adaptation. Each data point represents one test color.
In Figure 26, four out of ten color patches with relatively high lightness estimated at low luminance were statistically perceived as different brightness in single adaptation and mixed adaptation.
Three colors were perceived brighter in a single adaptation, while one test color was perceived brighter in a mixed adaptation.
Figure 26 Brightness estimation in single adaptation and mixed adaptation under Low Luminance Lighting
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Response in Mixed Adaptation (Low luminance)
Response in Single Adaptation (Low luminance)
Figure 27 Brightness estimation in single adaptation and mixed adaptation under High Luminance Lighting
In Figure 27, four of the ten test colors estimated at high luminance were significantly different between the two adaptations. The response of the mixed adaptation for all four test colors was perceived to be brighter than that of the single adaptation.
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Response in Mixed Adaptation (High luminance)
Response in Single Adaptation (High luminance)
4.4.3 Effect of adaptation condition on colorfulness estimation
The colorfulness of set E colors were estimated at low luminance and set F colors at high luminance in both adaptation conditions. In Figure 28, Figure 29, the horizontal axis represents the average response of the colorfulness estimation for the test color in a single adaptation. The vertical axis represents the average response of the colorfulness estimation for the test colors in mixed adaptation.
In Figure 28, the colorfulness estimation of set E in low luminance was made in single adaptation and mixed adaptation situations. The colorfulness response points of each color appear adjacent to the 45° line. The two out of ten test colors showed a significant difference in colorfulness estimation according to the adaptation. Both colors were perceived as less colorful in mixed adaptation.
Figure 28 Colorfulness estimation in single adaptation and mixed adaptation under Low Luminance Lighting
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Response in Mixed Adaptation (Low luminance)
Response in Single Adaptation (Low luminance)
Figure 29 Colorfulness estimation in single adaptation and mixed adaptation under High Luminance Lighting
In Figure 29, the changes in colorfulness estimation according to the single adaptation and mixed adaptation of the colors estimated under high luminance lighting are shown.
The test colors of the set F did not show a significant change in the colorfulness estimation according to the adaptation. Significant differences were found in only two out of ten colors, and colors were perceived higher in single adaptation than mixed adaptation.
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Response in Mixed Adaptation (High luminance)
Response in Single Adaptation (High luminance)
4.4.4 Summary of Effect of adaptation condition
Changes in color appearance with adaptation were investigated in terms of hue, brightness, and colorfulness. Hue of the GB test color was observed to be bluish in the mixed adaptation than single adaptation for both luminance levels.
In the estimation of brightness, it was estimated that at low luminance, three out of ten colors have a higher brightness in the single adaptation than mixed adaptation. However, since one color was estimated to have more brightness in mixed adaptation, it is difficult to say that the perceived change in brightness according to the adaptation under low-luminance lighting follows some trend.
Under high luminance lighting, four out of ten colors were reported to appear significantly brighter in the mixed adaptation than in the single adaptation. Therefore, it can be considered that at high luminance, colors may appear brighter in a mixed adaptation than in a single adaptation.
In the estimation of colorfulness, two out of ten test colors were perceived as higher colorfulness in single adaptation for both low and high luminance.
In the estimation of hue, brightness, and colorfulness, the color change with adaptation was significant for several colors. However, the number of color that changed with adaptation did not exceed the majority, and also because the direction of change was not constant, it cannot be confirmed that the change in appearance of the test color is due to the change in adaptation.