Reported are computation results for the spectral and integrated albedo, transmittance and absorption of solar radiation and long-wave absorption by low clouds with different water-to-ice-content ratios ranging from purely water to crystal clouds, the ice crystals widely varying in size. The effect of the crystal size and density on the albedo and absorption profiles for a fine vertical resolution was studied. It is shown that the integrated albedo is formed across the whole depth of the cloud layer and decreases with the increase of the crystal size at a greater rate than the absorption does. The calculated relations of the radiative characteristics to the cloud microstructure may be used as a basis for the development of parametrization.