Some species have at least 16 different photoreceptor types , 12 of them for color analysis in the different wavelengths ( including four which are sensitive to ultraviolet light ) and four of them for analyzing polarised light . Some species have at least 16 different photoreceptor types , which are divided into four classes ( their spectral sensitivity is further tuned by color filters in the retinas ) , 12 of them for color analysis in the different wavelengths ( including four which are sensitive to ultraviolet light ) and four of them for analyzing polarised light .