Table 3. Comparison of L, a* and b* values for images with post processing white balance correction using gray card.
| L | |||
| Median (IQR) | χ2 (df) | p * a | |
| Spectrophotometer (control) | 62.45 (7.80) | 156.875 (5) | p = 4.346 × 10−45 |
| Photo box | 50.00 (15.75) | ||
| Windowless clinic 1 | 54.00 (12.75) | ||
| Windowless clinic 2 | 57.00 (14.00) | ||
| Windowed clinic 1 | 72.00 (14.00) | ||
| Windowed clinic 2 | 60.50 (13.75) | ||
| a* | |||
| Median (IQR) | χ2 (df) | p * b | |
| Spectrophotometer (control) | 7.00 (5.10) | 281.707 (5) | p = 3.076 × 10−11 |
| Photo box | 15.00 (3.00) | ||
| Windowless clinic 1 | 11.00 (3.75) | ||
| Windowless clinic 2 | 11.00 (3.00) | ||
| Windowed clinic 1 | 13.00 (2.00) | ||
| Windowed clinic 2 | 13.00 (2.00) | ||
| b* | |||
| Median (IQR) | χ2 (df) | p * c | |
| Spectrophotometer (control) | 43.20 (10.68) | 235.572 (5) | p = 4.332 × 10−14 |
| Photo box | 22.00 (4.75) | ||
| Windowless clinic 1 | 23.00 (3.00) | ||
| Windowless clinic 2 | 25.00 (4.00) | ||
| Windowed clinic 1 | 26.50 (4.00) | ||
| Windowed clinic 2 | 26.00 (4.00) | ||
*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 < 0.001). Spectrophotometer vs all other lighting conditions showed highly significant differences (p < 0.001) except windowed clinic 2 (p = 0.185). No significant differences observed for photo box vs windowless clinic 1 (p = 0.217), windowless clinic 1 vs windowless clinic 2 (p = 0.125)
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). No significant differences observed for windowless clinic 1 vs windowless clinic 2 (p = 0.510), windowed clinic 1 vs windowed clinic 2 (p = 0.834).
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). No significant differences observed for photo box vs windowless clinic 1 (p = 0.303), windowless clinic 1 vs windowless clinic 2 (p = 0.175), windowed clinic 1 vs windowed clinic 2 (p = 0.192)