Comparison of digital photography and spectrometry for evaluating colour perception in humans and other trichromatic species

Yang, Chen, Wang, Jie, Lyu, Nan and Lloyd, Huw (2021) Comparison of digital photography and spectrometry for evaluating colour perception in humans and other trichromatic species. Behavioral Ecology and Sociobiology, 75 (11). 151. ISSN 0340-5443

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Abstract

Digital photography and spectrometry are widely used for colour measurement, but both methods have a number of advantages and disadvantages. Comparative studies can help determine the most appropriate method for quantifying animal colour perception, but few have attempted to compare them based on colour model conversion. Here we compare colour measurements from digital photography and spectrometry in a controlled standard experimental environment using the three-dimensional colour space model CIE L* a* b* which is designed to approximate colour perception in humans and assess the repeatability and agreement of the two methods. For digital photography, we first extracted RGB values from each colour patch and transferred these to L* a* b* values using colour model conversion. For spectrometry, we measured the spectral reflectance (SR) value and subsequently transferred SR values to L* a* b* values. Using a consensus of correlation analysis, intraclass correlation coefficients, concordance correlation coefficients, and Bland-Altman analysis, we found that although spectrometry showed a slightly higher repeatability than photography, both methods were highly repeatable and showed a strong agreement. Furthermore, we used Bland-Altman analysis to derive the limits of agreement, which can be used as criteria for identifying when photography and spectrometry could be as a suitable alternative for measuring colour perception in humans and other trichromatic species. We suggest that our workflow offers a practical and logical approach that could improve how we currently study colour perception in trichromats.