Blurry vision underwater is due to pupil dilation, which can be controlled to see as if wearing mask

[tursiops]

It is nowhere near a "pinhole," which does not have infinite depth of field anyway unless it has zero opening. The eye focal length is about 1.7 cm, and the smallest the pupil can get is about 2mm (in really bright light), so it is equivalent to a f-stop of 17/2 >> f/8.5. The eye can open to maybe 6 mm, so a wide-open eye is about f/2.8. Camera lens typically go to f/22, sometimes f/32, rarely f/45. So it is stopping down quite a bit if the eye goes to 2mm, but not nearly enough to make things sharp underwater. Maybe a little less blurry because of the increased depth of field at f/8.5 vs f/2.8, but not sharp. And it will be darker by a factor of 9. The original video is bunkum.

 

[lowviz]

17/2 ?

 

[tursiops]

17/2 ?

oops. Slip of my fingers. I'll correct it. Thanks!

 

[lowviz]

No prob, doesn't change anything...

 

[John C. Ratliff]

It is important to note that the Nautilus eye is without a lens, and that the organism itself is not dependent on sight for much of anything, there not being much light down there anyway. With a very narrow field of vision, it can "see" the phosphorescence of it's intended victim, but doesn't need visual information to find prey; water vibrations, to which it is probably very sensitive, will give that to the Nautilus.

Now, about our eyes, stopped down still doesn't help much, as we have that lens sitting there, which further refracts the light. This lens can focus (better for you than for me, at age 72 things don't focus as well).

"...The eye focal length is about 1.7 cm..." Well, I believe that this distance is from the center of the lens to the retina. But note that this focal length can be changed by the muscles around the eye's lens, unless the person has had cataract surgery, in which case another set of lenses are needed to change this focal length (glasses).
The Evolution of Vertebrate Eyes

SeaRat

 

[lowviz]

...//... Now, about our eyes, stopped down still doesn't help much, ...

Well, depends on what you want. I used to be nearsighted for 60+ years of my life. I couldn't read the clock in the bedroom without first finding my glasses.

So, I would pinch my thumb and forefinger of one hand together and add to that, the forefinger of my other hand. Creates a really nice adjustable pinhole. Could thus read the time clearly, but only because the digits were very bright. As one gets closer to cataract surgery (outpatient and trivial procedure), the pinhole effect will be increasingly effective.

Problem is, the very LAST thing that I need is less light.

 

[tursiops]

Cataracts were one of the best things that have ever happened to me. I got my first glasses at 9 yrs old, to correct myopia (near-sighted). 65 years later both eyes had the lens removed and multifocal implants inserted. Insurance paid for the procedure, but I had to pay the difference between single focal-length lenses and the multifocal ones. Good decision! I'm now seeing 30/20, near and far. No glasses. Changed all my prescription masks to plain glass. Happy happy. For the curious, the multifocal lenses are shaped like little hurricanes, with two spiral arms. The eye muscles push on those arms, and slightly deform the lens to focus it. Took my brain a couple of days to figure it all out.

 

[lowviz]

I went with single focus. I wanted the very best possible distance vision. Got it. You and I know that the quality of one's correction depends totally on one's ophthalmologist/eye surgeon.

I am active and tend to need eye protection so I went with 20/20 in both eyes figuring that I will always wear glasses. I asked for overcorrection, but he wouldn't do it. Said he was doing me a favor. Probably was, IDK.

If I forget my reading glasses, the finger pinhole thing works for near vision too. Ain't life a bitch...

 

[John C. Ratliff]

I went with single focus. I wanted the very best possible distance vision. Got it. You and I know that the quality of one's correction depends totally on one's ophthalmologist/eye surgeon.

I am active and tend to need eye protection so I went with 20/20 in both eyes figuring that I will always wear glasses. I asked for overcorrection, but he wouldn't do it. Said he was doing me a favor. Probably was, IDK.

If I forget my reading glasses, the finger pinhole thing works for near vision too. Ain't life a bitch...

You are right, as I just tried the pinhole effect for reading without glasses. I am now farsighted, and need blended trifocals to read easily. I attribute the fact that I have used the UV adjustable coating on all my glasses since that was an option for the fact that I still have my original, biological lenses in my eyes at this age.

SeaRat

 

[tarponchik]

You are right, as I just tried the pinhole effect for reading without glasses. I am now farsighted, and need blended trifocals to read easily. I attribute the fact that I have used the UV adjustable coating on all my glasses since that was an option for the fact that I still have my original, biological lenses in my eyes at this age.

SeaRat

I'm done with this multifocal nonsense and just buy cheap +2.0 glasses in WalMart, $9/pack of 3. I use them both for reading and computer and I see no difference. Long distance wise, my pinholes still work just fine