The lens in the eye actually has different curvature on the front and rear surfaces, so it functions a bit like a compound lens. The simple lens formula may be a useful approximation, but it doesn't tell everything.
Oh bother. And actually the cornea, and the chamber between cornea and lens, are parts of the optical train as well. The refraction starts at the corneal chamber, and the lens finalises the process. But, I still think that the simple lens formulas can be used as a first approximation.
The rods and cones have definitely different sensitivities. That's why color vision only works in sufficient light. But it's not as simple as that: the sensory organs are all a great big feedback-feedforward-feedacross networks. The retina adapts to the average illumination of the scene, and the individual neurons will detect differences from the average. More light will mean more contrast, so the pupil-widening reflex is still useful.
At least for the ear, the brain can control the "average background" adaptation. When you are about to blow a whistle, the ear will automatically damp down milliseconds before the blast. When someone behind your back blows a whistle without you knowing the moment, the dampening happens tens of milliseconds after the attack. Am not sure if I've seen anything about similar process being possible for the retina; would not be surprised, though.
![[identity profile]](https://www.dreamwidth.org/img/silk/identity/openid.png){kind=small}
Oh bother. And actually the cornea, and the chamber between cornea and lens, are parts of the optical train as well. The refraction starts at the corneal chamber, and the lens finalises the process. But, I still think that the simple lens formulas can be used as a first approximation.
The rods and cones have definitely different sensitivities. That's why color vision only works in sufficient light. But it's not as simple as that: the sensory organs are all a great big feedback-feedforward-feedacross networks. The retina adapts to the average illumination of the scene, and the individual neurons will detect differences from the average. More light will mean more contrast, so the pupil-widening reflex is still useful.
At least for the ear, the brain can control the "average background" adaptation. When you are about to blow a whistle, the ear will automatically damp down milliseconds before the blast. When someone behind your back blows a whistle without you knowing the moment, the dampening happens tens of milliseconds after the attack. Am not sure if I've seen anything about similar process being possible for the retina; would not be surprised, though.