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Thread: What focal length is your vision?

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    Default What focal length is your vision?

    Hi,

    Not sure if any of you tried this before, but I was trying to practise visualization using my eyes only and match it to the focal length that I was using. I found out that I could bearly visualize at the peripheries of my eyes what would be a 24mm wide view.

    Anyone got comment on how to develop this possible technique further, so that it can be useful when we walk around taking photos?

    chgoh @ 2:04 pm, 13 December 2004

  2. #2
    Senior Member sammy888's Avatar
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    Really? 24mm?

    I have been brought to understand since the day I took up photography years ago that the 50mm lens is the closest "approximate" to the human eye's perspective. It is usual lens they compare that too. 24mm is really too wide and gives a whole difference perspective view comapred to your eyes.

    I suspect you had your 24mm or some zoom lens mounted on a DSLR while you were testing that theory out?

    Btw..what did you mean by "being useful" for walk about shooting?
    Last edited by sammy888; 13th December 2004 at 02:34 PM.

  3. #3

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    I mean all the way to the peripheries, where you could detect vision. Kind of like can see, cannot see, corner of your eye perception.

    What is in my direct vision field is narrower. Not sure if its 50mm though.

    The experiment can be done. Just mount a lens and use it alternate with the naked eye to compare what is the vision field. Happen to have a 24mm mounted on a film camera that time, so I was quite surprized.

    For street photography, I guess this would be useful. Don't have to constantly bring your camera up to eye level. Quickly, size up the image you want, set it on the zome lens, guesstimate the exposure and distance, then fire away. Less intimidating I guess.

    chgoh @ 2:36 pm, 13 December 2004



    Quote Originally Posted by sammy888
    Really? 24mm?

    I have been brought to understand since the day I took up photography years ago that the 50mm lens is the closest "approximate" to the human eye's perspective. It is usual lens they compare that too. 24mm is really too wide and gives a whole difference perspective view comapred to your eyes.

    I suspect you had your 24mm or some zoom lens mounted on a DSLR while you were testing that theory out?

    Btw..what did you mean by "being useful" for walk about shooting?
    Last edited by chgoh; 13th December 2004 at 02:40 PM.

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    If you dig up some bio facts about human eyesight, i think you'd discover some like this:

    - human peripheral vision is greater than 180deg left/right. Wider than any fisheye. You can't focus on what's slightly behind you, but you can detect if there's motion there.

    - the centre part of the eye is a 'spot focus' effect. Even when reading a page, you can only focus on one 'spot' at one time.

    The '50mm is closest to human eye' approximation actually comes from the magnification, not the focal length. Meaning that for most SLRs (then), the 50mm lens provides a view that is most similar in size to what the eye sees. This, of course, varies with different viewfinders. Some point&shoot actually magnify the viewfinder a lot, which others are a bit on the small side.

    For street shooting, i would draw the angles of view on a small piece of paper (about 1cmx1cm) and stick it on top of the camera.

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    Senior Member sammy888's Avatar
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    Well there is the explanation given that you are seeing alot more with your eyes and maybe while comparing to a 50mm lens but then again you are looking with your naked eyes in "stereo" Two 50mm eyes each being able to see the more extreme left or right respective of each eye ball.

    And there is also how the way your brain is wired. Your brain actually has the ability to "self-correct" in certain situation.

    As for wanting to shooting without looking into the camera. It does not have to really be similar to your eye angle of view. I have done alot of that off the cuff shooting for along time. I usually have to fire off a few shots and at high speed too. Just holding it in your hand as you walk..you tend to sway your body according to your steps...thus your hands will be shaking and swinging. Not a good position to take steady shots and if you start to hold it stiffly in your hands and you stop moving, people will know you are shooting something. The fact that you have a camera infront of you will casue them to look at you and what you might be doing. There is also the AF. Depending on how close you are to the subject and the surrounding area...it might get your AF focus on the wrong things or it just will not fire if it can not lock in to one. And you go, pressing your buttons all the time and trying to now move your camera around at maybe hip level hehe... I have done all that stuff and I have been spotted often. I do get some nice candid but most are wasted in some way. Easier to use a super long lens or to just go up and shoot. I now do it very naturally...I dont try to hide or be sly about it and I shoot with a body languauge that tells people I am doing this as an interest in photography and am trying to capture an interesting scene. And sometime you just need to communicate that too. In fact I offer to send them the pictures too which helps to make friends and also get them more comfortable. Anyway it is not like I am shooting some embrassing or morbid scene.

    But you can still do that...having your camera at hip level with your left hand to stablise it against the neck strap and with your finger on the trigger or with a remote to trigger the shutter. But something like 24mm in a 35mm camera is pretty far. If you get anything it might be too far and you might need to crop into those interesting bits of the picture.

  6. #6

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    Some thoughts (not facts) about human vision:

    1. When comparing angle of view, it's important to consider the surface area of the sensor involved. Obviously, a 50mm lens will have a different angle of view on a full frame sensor as it would on a 1.6X FLM sensor. We all know this. A 50mm lens on 35mm film gives roughly the same perspective as a 75mm lens on a medium format film. We all know this also. So it's quite useless to talk about focal length of the human eye unless we standardize to refer to 35mm film systems (or 135 format, as they are otherwise known). If you really must compare the human eye sensor area to your 1.6X FLM sensor, here's a useful reference:

    http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract

    Interesting that the sensor appears to be about 50 megapixels. Technology has some way to go to catch up.

    2. It should also be noted that the sensor area in the human eyeball is laid within a sphere, rather than a flat plane. This will of course affect the optical calculations (and probably why we don't experience chromatic aberration!). The closest would be one of those curved plane panoramic cameras which only offstoners are interested in.

    3. DOF of my personal lenses seems to be pretty great. Very hard to get decent bokeh except when eyeballing at macro distances without my glasses. Yet focusing on a subject and ignoring the background seems very easy to do. I think it's because of the brain performing sensory focus. That's how a lot of advertising works. All you need is a girl in a bikini.... but I digress.

    4. And of course, ISO is infinitely variable. Thank God for my eyes!

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    uh, i think popular literature has it that the *perspective* of our eyes are about that of the 50mm lens, but the angle of view, like metioned, can be really really wiiiiiide... just try crossing your eyes. seeming a larger covered angle, but cannot focus...

  8. #8

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    Quote Originally Posted by chgoh
    Hi,

    Not sure if any of you tried this before, but I was trying to practise visualization using my eyes only and match it to the focal length that I was using. I found out that I could bearly visualize at the peripheries of my eyes what would be a 24mm wide view.

    i agree

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    Default Simple way to test FOV

    A rough way to test angle of view for one or both eyes.....

    1) Focus on a spot straightahead, a reasonable distance away
    2) Stick out both arms horizontally out to your sides palms facing upwards, forming a 180 degree plane finger to finger.
    3) Wriggle your fingers whilst moving the arms simulataneously forwards slowly.
    4) When you detect movement with your perpheral vision, stop. Voila! You've got a rough estimate of your angle of view.

    Cheers,

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