>>122560369Not sure about IR, but human retinas are sensitive to UV. However, the lens filters that out.
People with artificial lenses (replacing ones clouded by cataracts) can see UV. Salt and sugar and flour look entirely different.
During WW2, the British employed such pensioners to watch the coast of France, just in case the Nazis were sending instructions to spies and saboteurs in the UK via UV blinkers.
Our vision does work like a camera, especially modern ones with CCDs. But there's a great deal of "signal processing" along the optic nerve before the information reaches our visual cortex. We can't control that so we can't sharpen, amplify, magnify, or apply false colors at will.
In fact, human eyes are rather poorly designed. The light-sensitive face of the retinal cells is on the _back_ side. Light has to pass through those cells before being detected and, of course, some is absorbed and scattered in the process. The "cable", the optic nerve", emerges on the _front_. They gather together, further blocking light, and then plunge through the retina. That's why we have a "blind spot" which our minds "fill in".
Cats have a reflective layer behind their retinas. Light which isn't absorbed on the first pass gets a 2nd chance. So cats can see in dimmer light than we can. But, because the light comes from different distances, both cannot be in focus simultaneously. So what they see is somewhat blurred compared to our vision.
https://www.popsci.com/article/science/see-world-through-eyes-cat/ shows comparison images.
