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