A method of quantifying melanin includes receiving at a data processor optical data produced by an optical sensor which receives a light from a tissue determining a set of intensity values based on the optical data for each intensity value, converting the intensity value to a quantifying value corresponding to quantity of melanin in the tissue based on a two-dimensional non-linear regression with one variable representing the intensity value and another variable representing the quantity of melanin collecting at the data processor each quantifying value generating at the data processor melanin quantity distribution data according to the quantifying values and outputting the melanin quantity distribution data to be presented on a medium.
