J. Butts1, R. Seelaus1, D. Morris1 1University Of Illinois At Chicago,Plastic Surgery,Chicago, IL, USA
Introduction:
Accurate color measurement is essential to the plastic surgeon desiring optimal aesthetic outcomes. Variability of human perception and environmental lighting conditions limit observation or swatch-based methods, leading to use of spectrophotometers as the gold-standard for accurate color matching.
Advances in smartphones camera technology and the utilization of device-independent color-spaces may provide an opportunity for replacement of spectrophotometers in resource-limited settings, without significant calibration or processing.
We investigated the utility of a consumer smartphone camera against a spectrophotometer for the evaluation of skin tones in a variety of illuminant environments.
Methods:
Silicone disks pigmented to match a representative skin sample from a fair-skinned subject were created using spectrophotometer measurements in standard fashion. Skin and disk samples were measured with the spectrophotometer and imaged with a smartphone under three illuminant conditions: D65 (simulated daylight), incandescent, and white fluorescent TL84.
Average pixel RGB values of each silicone and skin sample were calculated from each smartphone image. Samples were converted from sRGB to Lab color-spaces, and Euclidian distances (dE) were calculated between matched skin and silicone Lab samples.
Results:
A two-way one sided t-test was performed to assess equivalence between mean spectrophotometer and smartphone values. A magnitude threshold of 1.0 was chosen as a maximally-stringent, just noticeable difference in fair-skinned individuals.
Images taken under D65 were statistically equivalent to the spectrophotometer. Those under incandescent and fluorescent were not, with incandescent providing lower, and fluorescent higher, dE values.
Conclusion:
Equivalence between smartphone and spectrophotometer under simulated sunlight agrees with recommendations for indirect sunlight as an ideal condition for color matching. Although incandescent and fluorescent narrowly-missed equivalence, their precision suggests utility if measurements are taken in consistent lighting conditions or for applications with greater tolerances.