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Vision problem! who's right?

by neden
Tags: vision
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Oct16-10, 06:08 PM
P: 18

I don't know if this is a stupid question but one day me and my friend were talking and we got into an argument about viewing a screen through a camera's phone and a phoropter with the same lense in both. Suppose that the lense is perfect for my eyesight and suppose that we have completely different strength in eyesight; I cannot see objects clearly without my glasses but he can. So when we visit the optometrist office and try to view images under that very same lense, it is suitable for me but not for him. Now in the case of viewing the screen under a camera, would it yield the same result? My friend insists that yes because in this case we will both be able to visualize the images on the display screen on the camera at the same quality because we are both viewing images under the same specifications set by the camera and because of this, therefore our eyes do not need to adjust at all because the camera does all the conversion behind the scenes.

So who's right? He says under the camera we will see the same thing but I say we wont because the lense should only work for me (since if it never worked for him in the optometrist's office it will not work on a camera's screen), I am no physicists but can anyone kindly explain this?
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Dr Lots-o'watts
Oct16-10, 08:13 PM
P: 674
The camera focuses the image on a chip, so it takes care of the long-distance-focusing for both of you.

Now whether you can see the image clearly on the camera screen or not depends on how well your eyes can focus on small distances.

Some people can focus better on long distances than on short ones, and vice versa.
Oct17-10, 12:34 AM
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Pythagorean's Avatar
P: 4,292
It depends on how bad your visions is (assuming you're near sighted). From the proprortions in your picture, for instance, at that distance, I wouldn't be able to make out what was on the camera/cellphone, so you'd be correct if the cell phone is really that far away. If you and your friend both held the phone close to your faces, so that you overcame the astigmatism, then your friend would be correct, neither of you have to use your long-distance focus when the screen is right there.

Oct17-10, 03:41 AM
P: 18
Vision problem! who's right?

So basically now whatever I view on the camera at that specific lense that may turn out to be perfect for my vision does it also mean that it will also perfectly work for him? The answer is no, right? Even though the camera has done all the work for us, we still have our own subtle differences in eyesight.

Basically what I'm trying to say is that even after the camera has done all the work for us, we both still won't be seeing the same thing on the camera (the camera will not correct both our visions at the same time thus we will not be seeing the image with the same visual quality; the answer seems trivial but I just want to get that through my head).
Dr Lots-o'watts
Oct17-10, 05:05 PM
P: 674
The camera focuses a perfect picture on its chip from a distance d1 (camera - object). The "perfection" of this picture is completely independent of anyone's eyesight.

Now when you look at the picture on the camera, your eyes have to focus a new distance d2 that is much smaller than the distance d1 of the real object. The situation is now completely independent of d1. The details of the picture on the camera screen are focused by your eyesight exactly as if they were details of the camera casing, buttons, brand name label, tripod, or the finger nails from the hands that are holding it.
Oct18-10, 01:24 AM
P: 18
Thank you, that particular explanation makes sense.

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