Makeshift pinhole with your fingers to see better.
Posted , 3 users are following.
You know that focus becomes much less critical when you view through a pinhole. I wanted to point out that we have a pinhole available to us for shopping etc. If I want to read the ingredients of a food while shopping, I use the tips of my thumb and index fingers, along with the (medial) side of the side of the farthest (distal) middle finger segment to form a triangular pinhole that I hold close to my eye. The middle joint of my thumb goes next to my nose.
Similarly, the impromptu pinhole can also allow a nearsighted person to see farther details on a sunny day.
The brighter the light, the better this works.
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RonAKA trilemma
Edited
Yes, that is why people squint to improve their vision. When one squints it is a sure sign new glasses are needed... And that is why the paddle with the pinholes are used in a quick and dirty eye exam. If looking through a pinhole improves vision then a refraction change is usually needed.
Guest trilemma
Posted
What a pinhole essentially does is it blocks out the light coming in from the most extreme angles so most of the light comes in at a straighter angle. The steep angled light is more challenging to focus.
trilemma Guest
Edited
An off-center pinhole is probably still going to help acuity. But with a pinhole you do with your fingers, the pinhole undesirably gets farther from the cornea. To experiment angles off of the centerline , I would make a pinhole with a pin in aluminum foil. Your high-res cones (color eye pixels) are near the midline of the eye, so I think the falloff would mostly be due to that.
I would say that it makes the eye more like a pinhole camera or a high-F-stop lens, but another factor is that it limits the rays to using part of the cornea. Any dents and aberrations in the cornea are not going to work against you.
The point of my post is that you have a pinhole handy.