Why does it take so long for your eyes to adjust to the dark, but very little time to adjust to light?
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Muscles only work in one direction…they can pull, they can’t push. The only thing they can do to get longer is relax and let other forces (frequently a different muscle) pull them longer.
Your iris, the part of your eye around your pupil, has strong muscles to contract (make your pupil smaller) but not as strong to pull them open. So your eyes can contract *very* quickly to cut down bright light coming in but they can’t dilate very fast to allow more light in when it’s dark. And the reason that’s not that important is…
You have two different kinds of light sensors in your eyes. “Cones” can detect color but only work well in bright light. “Rods” only see black & white but work well in low light. In order to work, rods use a very light sensitive chemical that’s completely blown out when you’re in bright light. We continuously make more of it all the time but not that quickly…when you’re in bright light you’re basically starting from zero as far as “rod fuel” because it’s destroyed as soon as it’s created. It takes time to build up enough that your rods start to function properly.
The combo of the two means that it takes several minutes for your dark mode eyes to work properly, but in bright light your pupils can clamp down fast and your cones immediately have enough light to work with and can do their thing.
The cells in your eyes react to light when it hits photopigments that give electrical impulses. Rhodopsin is the night vision photochemical and light causes it to break down. Too much light and it is all gone. It takes a while for the eye to produce more.
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