The previously developed spectral transparency method is improved in two ways: (a) A calculation scheme is developed that enables the consideration of light dispersion within a substance. We abandon the assumption that m(ν) = const and develop a method of calculating N(r) from γ*(ν) provided that the function m(ν) is specified. (b) A new scheme of processing data on γ*(ν) is proposed that significantly reduces the oscillation in the answer and requires less initial experimental data.