Effect of cross-polarization filters on the trueness of colors obtained with a single-lens reflex camera, macro lens, and a ring flash

Abstract

ObjectiveTo investigate the effect of cross-polarization filters on the colors of shade tabs obtained with a digital single-lens reflex (DSLR) camera, macrolens, and a ring flash. Materials and MethodsDigital images of four shade tables (1M1, 3L2.5, 3R2.5, and 5M3) from the VITA Toothguide 3D-Master shade guide were taken using a DSLR camera, 100 mm macrolens, and ring flash with two different cross-polarizing filters (Polar_eyes and Filtropolar), and without (Nonpolarizer; n = 7). The CIE L*a*b* color coordinates of digital images were calculated and remeasured with a spectroradiometer (SR). The color differences (Delta E-00) between the SR and digital images were calculated and analyzed with the two-way analysis of variance (ANOVA) and Tukey HSD test (alpha = 0.05). Results Delta E-00 values of all test groups were higher than the clinically acceptable threshold ( increment E-00 > 1.80). While the increment E-00 values of Filtropolar (6.19 +/- 0.44) and Polar_eyes (7.82 +/- 0.23) groups were significantly higher than the Nonpolarizer (4.69 +/- 0.32) for the 1M1 shade tab, increment E-00 value of Polar_eyes (6.23 +/- 0.34) was significantly lower than Nonpolarizer (10.71 +/- 0.48) group for 5M3 shade tab (p < 0.05). ConclusionThe color-matching results of tested digital photography techniques with and without cross-polarization were unacceptable, compared to a spectroradiometer. While digital photography with Polar_eyes cross-polarizing filter has closer results to the reference device for the low-in-value shade table (5M3), for the high-in-value shade table (1M1), improved results were obtained without a cross-polarizing filter. Clinical SignificanceThe cross-polarization filters are increasingly used in dentistry for tooth color communication with digital photography techniques. However, the digital photography techniques with-without cross-polarization filterers should be improved to obtain clinically acceptable color-matching results.