"Our findings reveal that the specific spectral tunings of the four cone types near optimally rotate the encoding of natural daylight in a principal component analysis (PCA)-like manner to yield one primary achromatic axis, two colour-opponent axes as well as a secondary UV-achromatic axis for prey capture."
https://www.biorxiv.org/content/10.1101/2020.10.26.356089v1
"Our findings reveal that the specific spectral tunings of the four cone types near optimally rotate the encoding of natural daylight in a principal component analysis (PCA)-like manner to yield one primary achromatic axis, two colour-opponent axes as well as a secondary UV-achromatic axis for prey capture."