Table 1. Comparison of L, a* and b* values for images without any white balance correction (raw images).
| L | |||
| Median (IQR) | χ2 (df) | P* a | |
| Spectrophotometer (control) | 62.45 (7.8) | 226.691(5) | p = 4.682 × 10−62 |
| Photo box | 71.50 (9.8) | ||
| Windowless clinic 1 | 73.00 (10.8) | ||
| Windowless clinic 2 | 57.00 (15.0) | ||
| Windowed clinic 1 | 72.00 (7.0) | ||
| Windowed clinic 2 | 61.00 (12.8) | ||
| b* | |||
| Median (IQR) | χ2 (df) | p* b | |
| Spectrophotometer (control) | 7.00 (5.1) | 260.727 (5) | P = 1.267 × 10−17 |
| Photo box | 20.50 (3.0) | ||
| Windowless clinic 1 | 7.00 (2.0) | ||
| Windowless clinic 2 | 8.00 (4.0) | ||
| Windowed clinic 1 | 10.00 (2.0) | ||
| Windowed clinic 2 | 9.00 (3.0) | ||
| b* | |||
| Median (IQR) | χ2 (df) | P* c | |
| Spectrophotometer (control) | 43.20 (10.7) | 335.766 (5) | p = 1.201 × 10−19 |
| Photo box | 42.00 (2.0) | ||
| Windowless clinic 1 | 22.00 (4.0) | ||
| Windowless clinic 2 | 21.00 (2.8) | ||
| Windowed clinic 1 | 27.00 (5.8) | ||
| Windowed clinic 2 | 24.00 (3.8) | ||
*Significant < 0.05; χ2 = Chi-square statistics; df = degree of freedom, IQR = Interquartile Range
*Kruskal-Wallis one-way test: Parametric assumption not met. Shapiro- Wilk test significant (p < 0.05)
a Post-hoc analysis (Dunn’s test) for L: Null hypothesis rejected (p = 0.0 × 100 < 0.001). Spectrophotometer vs all other lighting conditions showed highly significant differences (p < 0.001) except windowed clinic 2 (p = 0.508). No significant difference was observed for photo box vs windowed clinic 1 (p = 0.303), photo box vs windowless clinic 1 (p = 0.258), and windowless clinic 1 vs windowed clinic 1 (p = 0.919)
b Post-hoc analysis (Dunn’s test) for a*: Null hypothesis rejected (p < 0.001). Spectrophotometer vs all other lighting conditions showed highly significant differences (p < 0.001) except windowless clinic 1 (p = 0.136). No significant differences observed for windowless clinic 1 vs windowless clinic 2 (p = 0.098) and windowed clinic 1 vs windowed clinic 2 (p = 0.208)
c Post-hoc analysis (Dunn’s test) for b*: Null hypothesis rejected (p < 0.001). Spectrophotometer vs all other lighting conditions showed highly significant differences (p < 0.001) except photo box (p = 0.985). No significant difference observed for windowless clinic 1 vs windowed clinic 2(p = 0.101)