Strange eye adjustment
Have noticed something that seems strange to me, not being an opthamologist.
When I stand for a prolonged time in "complete" darkness my eyes seem to become more nearsighted. When I tray-develope a sheet I have an opaque divider between the tray and a timer with "glow in the dark" numbers. This is connected to a radio that will go silent when time is up.
When I put out the light I can see the numbers very sharply but after about 4 minutes I notice that I have to lean closer to see the numbers. Just like being shortsighted.
I would think that as the eyes adjust I would be able to see better in the dark, not worse.
Anyone else noticed this?
The dark shows up problems faster because you pupils have far less depth of field, also your eyes relax..
It's why as your eyesight gets worse it becomes noticeable in low light levels. It's why people with failing sight & no glasses often use a bright light to read,, one of my friends uses a torch
It could be that your iris was wide open, thus, shorter depth of field. I noticed once that in bright sunlight I could focus closer than ever before, presumably because my iris was so small and I had great DOF.
Your eye is a lens, so the circle-of-confusion principles will apply just the same.
update.... JINX! You have fast fingers Ian Grant
Slightly OT but a lot of people let their circle of confusion envelope their whole head.
Why are there no speaker jacks on a stereo camera?
I resemble that!!!
Originally Posted by richard ide
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Hey, my darkroom is a room of confusion.... my confusion is bigger than yours.
Develop, stop, fix.... wait.... where's my film?
I'm an ophthalmologist, let me see through ;-)
What you experienced is very common , it's called night myopia and constitutes a shift of up to -0.5 diopters at low light levels. Reason: the lens is aspheric, outer regions that get revealed when the pupil dilates have a shorter focal length. Plus, as has been mentioned, an increase of aberrations with a wide pupil.
Erm... well, that's interesting. Very interesting. A bit OT again for interest...
How is it explained that I need glasses inside for reading/detail but can see perfectly well outside in most conditions, even for reading/writing — no specs necessary, amazingly. Is it the same as in the darkroom (though it's not dark in the house).
You're stopping down your eye when you go outside, smaller coc and so on. Break out your light meter, it IS darker in the house. Get a really strong reading light to equal the luminance you measure outside: presto, you can read again without glasses. But don't cheer too soon, this, too, will pass like all worldly things as presbyopia progresses.
Originally Posted by Poisson Du Jour
I'm near sighted and can no longer see close up in near darkness. Even with glasses it's hard to drive at night. Astigmatism causes flare in oncoming headlights.
I can't even read the date on a coin without a magnifier. Old age is fun isn't it. OK I'm not that old so call it middle aged.