4.3. Limitations
A limitation of this study is that only participants with skin tones of an intermediate color were included. Therefore, an improved model for a general skin tone should be investigated in future studies. To cover the full range of skin tones such as Fitzpatrick skin types I to VI, the model should consider the effects of melanin, and the features with additional wavelengths should be designed. To resolve this issue, using RRS as a reference should be carefully considered because the approach is affected by chromophores [To quantify the usual carotenoid intake, it is necessary to further examine whether the relationship between the equilibrium SCL and usual intake exists. However, both the 