Recent computational studies have revealed the critical impact of the electronic structure of the excited state species generated during the light-induced double bond isomerization of the chromophore of rhodopsin pigments. While a charge transfer structure dominates the function of visual rhodopsins (1), a diradical structure appears to control the fluorescence emission in NeoRhodopsin (3,4) and in a set of archaearhodopsin optogenetic reporters (2). By using a novel and unconventional type of quantum chemical modeling, we show that the stability of such a diradical must be inversely proportional to the absorption wavelength and that, most importantly, both properties can be regulated by the position and “delocalization” of the counter-ion of the protonated retinal chromophore.