I was reading that the maximum F number of a human eye, if treated the same way as a camera lens, would have an F number of 2.1, but basically since the eye cannot be treated the same way as a camera lens, the actual maximum aperture of what we see is about 3.2 (to put it shortly).
The glass of a lens absorbs a portion of the light that passes through and lowers the amount of light the camera receives. For example, my f/1.8 lens was rated a T number of 1.9 since it transmits as much light as a theoretically perfect f/1.9 lens would. I would assume that since the eye is filled with liquid not air like a camera lens, this could have a significant effect on its T Number. I was searching for a value of the T stop of a human eye, but I couldn't find anything on it. Does anyone know what it is or how it could be calculated?