Abstract
Statement of problem. Limited data are available in the dental literature regarding the effect of ambient lighting on the consistency of color quantification in cross-polarized photography.
Purpose. The purpose of this clinical study was to investigate the effects of ambient lighting conditions and postprocessing photograph calibration on color quantification in cross-polarized dental photography.
Material and methods. Twelve volunteers with intact maxillary central incisors were recruited. Cross-polarized photographs were captured under light-emitting diode (LED), fluorescent ceiling, and natural lighting. The photographs were repeated after a 1-week interval, yielding a total of 72 photographs. The average Commission Internationale de l'Eclairage L*a*b* coordinates of the right central incisor were obtained with a software program before and after calibration by using a neutral gray reference card. The color difference (Delta E) values were calculated for each participant between the repeated photographs under the change and no change in illumination both before and after calibration. A 3-way repeated measures ANOVA was used to compare these values (alpha=.05).
Results. A statistically significant 3-way interaction was found between the illuminant type, change in illumination, and calibration (P<.001); however, all the SE values were within a clinically acceptable threshold (Delta E <= 3.7). Before calibration, when photographs were captured under no change in illumination, LED lighting was found to have a significantly lower Delta E than fluorescent (P=.008) and natural and fluorescent lightings (P=.011), but when there was a change in illumination, no significant differences (P>.05) were found. After calibration, all the Delta E values were <= 1 and significantly lower than the values before calibration (P<.001).
Conclusions. Both the ambient illuminant type and change in illumination had minimal effects on Delta E. Calibration through the use of a neutral gray reference card was found to result in reduced and imperceptible color change (Delta E <= 1) for all illuminant types.