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10/15/2004 10:35:48 AM · #1 |
Clearly, our eyes are amazing optical devices. Some of the more amazing "glass" out there. :-)
Does anyone know what the "specs" are for our eyes? In particular, what f-stop are using. I presume it's fixed? Seems qualitatively maybe like f/4 or so? Pretty shallow DOF, really. I've spent 20 minutes on the train this morning refocusing my eyes at various focal distances, trying to see how it compares with using my camera. The one tangible outcome of my experiments is that I've got a bit of a headache!
There must be studies out there putting our eyes in photographic tech-geek speak. Anyone got links?
-Will
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10/15/2004 10:37:54 AM · #2 |
well the "lens" variable aperture (your iris!) and the "processor" is so powerfull that it's faster than any USM motor out there....and what about WB, instant on the nose adjustment...and what about focus point!
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10/15/2004 10:39:31 AM · #3 |
a very interesting idea, i hope someone can find some kind of study
-Mathyou |
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10/15/2004 10:40:13 AM · #4 |
our f-stop is not fixed. If it were, then our eyes wouldn't adjust to the dark. Picture this. When your eye "dialates", it's adjusting to allow more light in. Which means it's going from a 16 to a 5.6. Or is that 5.6 to a 16? I always get it backwards.
In terms of DOF...that's why some people need corrective lenses. They either have a deep DOF and not a shallow DOF, or visa versa. Near or Far Sightedness.
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10/15/2004 10:40:25 AM · #5 |
| Of course, the iris controls aperture. Does this mean that our vision has a deeper DOF when it's really light out because our eye "stops-down"? Whoa, that'd be cool! |
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10/15/2004 10:43:09 AM · #6 |
Originally posted by atsxus:
In terms of DOF...that's why some people need corrective lenses. They either have a deep DOF and not a shallow DOF, or visa versa. Near or Far Sightedness. |
It seems to be that's a function of focal distance. Folks who have perfect eyesight have the equivalent of a Canon 100mm macro lens, they can focus all the way from 1-to-1 to infinity without any special devices. For me, I'm near-sighted, so I have more like a WA on an extension tube. I can't focus past about 2 feet without my glasses! And for folks who are far-sighted, they have more like a 70-200. They can't see anything that's closer than about 3 feet without extra optics. |
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10/15/2004 10:46:59 AM · #7 |
You have a constantly-adjusting aperture (the pupil) which is determined by the iris -- the colored part of the eye, which is a muscle which controls the size of the opening.
The lens itself is suspended by a ring of ciliary muscle. As these contract or relax, the lens diameter is stretched or diminished, changing the curvature (and thus focal length). As the lens ages, its tissues become stiffer and harder to distort, leading to presbyopia or age-related farsightedness, as it becomes harder to change the shape of the lens to accomodate to nearby objects. Eyestrain, headache, and reading glasses are the most common manifestations. |
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10/15/2004 10:51:17 AM · #8 |
That's funny--we were just discussing this over on another forum.
We all did some googling and found that the focal length of the human eye is approximately 17mm. Of course, your pupil can dialate to let in more light, which means that it is not a fixed f/stop. We found this quote:
"the generally accepted diameter of a dark-adapted, fully-expanded pupil of a human eye" is 7mm."
That means that the max f/stop of a human eye is 7/17 = f/2.4.
I wasn't able to find anything on the minimum diamter though. |
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10/15/2004 10:56:47 AM · #9 |
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10/15/2004 10:58:00 AM · #10 |
Also, remember that if you're going to test your eye's 'depth of field' you can only use one eye.
With two eyes, our depth of field is incredibly small, as is our "width and height of field". |
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10/15/2004 11:03:23 AM · #11 |
Awesome, cpurser. Honestly, I figured I could find the answers on Google, but then what excuse would I have to refresh DPC all day at work on a slow Friday?! :)
These are great resources though.
To summarize one of them, it suggests that the focal distance is 17mm and the f-stop range is about f/2.5 to f/11
-Will
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10/15/2004 12:07:06 PM · #12 |
| The f-stop measure for the human eye isn't very meaningful by itself. On a camera, we often change the ISO rather than the f-stop. Well, for the human eye, the "ISO" range is orders of magnitude greater. In fact, the fully dark-adjusted human retina is right at the theoretical limit of sensitivity. We can see as well as cats in the dark. Our problem is that it takes the retina 20 minutes to get fully dark-adjusted. Today's city dwellers can go through their whole lives without ever reaching full dark-adjustment. Next time you are in the wilderness on a moon-less cloudy night, turn off all lights and wait a at least 10 min. First you loose color vision and then foveal vision (the center two or so degrees), but you'll be amazed at how much you can still see in what you first thought was pitch-black. |
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10/15/2004 12:08:05 PM · #13 |
| Our camera, the one eyed monster |
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10/15/2004 12:10:58 PM · #14 |
Originally posted by magnus:
The f-stop measure for the human eye isn't very meaningful by itself. On a camera, we often change the ISO rather than the f-stop. Well, for the human eye, the "ISO" range is orders of magnitude greater. In fact, the fully dark-adjusted human retina is right at the theoretical limit of sensitivity. |
What about owls and such? I thought their sensitivity was much higher??
Message edited by author 2004-10-15 12:11:05. |
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10/15/2004 02:47:57 PM · #15 |
Originally posted by ericlimon:
Our camera, the one eyed monster |
That's what my wife calls something else...
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10/15/2004 03:16:21 PM · #16 |
Originally posted by thatcloudthere:
Originally posted by magnus:
The f-stop measure for the human eye isn't very meaningful by itself. On a camera, we often change the ISO rather than the f-stop. Well, for the human eye, the "ISO" range is orders of magnitude greater. In fact, the fully dark-adjusted human retina is right at the theoretical limit of sensitivity. |
What about owls and such? I thought their sensitivity was much higher?? |
That is a good question. The eyes of Owls and Hawks must have the ability to change focal length almost like a zoom lens.
On another note this is one of the most interesting forums I have seen in a while great job wkoffel, thank you for giving me something to pass the time while wait here at work for this endless friday to be over and the weekendto be here. |
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10/15/2004 03:24:47 PM · #17 |
Originally posted by thatcloudthere:
Originally posted by magnus:
The f-stop measure for the human eye isn't very meaningful by itself. On a camera, we often change the ISO rather than the f-stop. Well, for the human eye, the "ISO" range is orders of magnitude greater. In fact, the fully dark-adjusted human retina is right at the theoretical limit of sensitivity. |
What about owls and such? I thought their sensitivity was much higher?? |
Well, I remember something about a study where people could detect a blinking light in an absolutely dark room, even when the light had been calibrated such that only about 0-5 photons actually reached the eye per light-blink. That's pretty close to the limit of seeing individual photons, which is as good as any theoretical detector can do. |
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