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Human eye

  1. Jul 19, 2004 #1

    wolram

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    Can someone tell me how fast the human eye can capture an
    image?and how fast it can notice a change, " notice a pinprick
    of light", for instance. :smile:
     
  2. jcsd
  3. Jul 19, 2004 #2

    chroot

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    From what I've read, the eye takes exposures about 1,000 times a second. I cannot provide any references at the moment, unfortunately.

    - Warren
     
  4. Jul 19, 2004 #3
  5. Jul 20, 2004 #4

    wolram

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    Thankyou Warren, jeebus.
    I have found various figures but nothing concrete, i would have thought
    the armed forces a good place to start to look for research, but i found
    zero.
     
  6. Jul 20, 2004 #5

    Njorl

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    I don't know how fast it can go, but old images persist for about 1/16th of a second. I doubt a new image can be written much faster than this. I did a neat experiment. Put a weight on a white string, whirl it real fast (>16 rotations per second) and you can show a movie on it. I think most movies run at double this speed though, anout 32 frames per second.

    Njorl
     
  7. Jul 21, 2004 #6
    "Some answers"

    http://www.100fps.com/how_many_frames_can_humans_see.htm :smile:

    Did you ever notice that the refresh rate of computer monitor, is captured quite differently, by the human eye, as seen though a TV screen? The refresh rate of a good monitor is 100 fps, so we perceive a still image. When we view the monitor through a TV, that is 25 fps, the image is shattering, refreshing 4x slower than if we would view it in direct. I believe, so we could put different fps monitors and different TV fps screens combinations and in theory see the difference by visual inspection, we could count the amount of shattering in 1 second with a simple stop watch.

    http://medfmt.8k.com/mf/eye.html
    A Russian scientist and academician tested the sensitivity of retina, it can sense as few as a dozen photons.
     
    Last edited: Jul 21, 2004
  8. Aug 5, 2004 #7
    Believe it or not, the frame rate the human eye can perceive is only around 14-16 frames per second; this is generally why motion pictures are captured at 30 frames per second; because that compensates for non-synchronizing to refreshing... this is also why you can't really guess the frame rate of a live picture if its above 35 or so.
     
  9. Aug 5, 2004 #8

    wolram

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    fafalone
    Imagine yourself in a very dark room. You have been there for hours and it's totally black. Now light flashes right in front of you. Let's say as bright as the sun. Would you see it, when it's only 1/25th of a second? You surely would. 1/100th of a second? Yes. 1/200th of a second? Yes. Tests with Air force pilots have shown, that they could identify the plane on a flashed picture that was flashed only for 1/220th of a second.
    Just what i wanted, thanks. The corrs are great.
     
  10. Aug 5, 2004 #9
    I think that this link can be useful for you
    http://webvision.med.utah.edu/
     
  11. Aug 5, 2004 #10
    The human eye can detect 1 photon.
     
  12. Aug 5, 2004 #11
  13. Aug 6, 2004 #12
    Hey, I'm new here - poking around after a fiery debate with a room-mate about gender differences in eyesight. I was claiming male and female brains process the information gathered by the retina differently. Granted, I just now made this up but I think it might be based on something I may have read somewhere.

    Anyway, he got extremely pissed off and began howling that male and female eyes are exactly the same and any difference in eyesight had to be based on environmental factors or upbringing or some such nonsense.

    Can anyone refer me to some kind of solid study I can use to relentlessly destroy the foundation of his belief? And is this a whole new thread? I thought it was vaguely related to the topic above...
     
  14. Aug 7, 2004 #13
    To see distinct frames and events requires not only the rod/cone cells reacting, but also the entire visual pathway and processing areas, so the real answer is really not as large as you think since it's quite a complex pathway and nerve signals don't travel that fast.
     
  15. Aug 8, 2004 #14
    I was going to say this but did not want to make a claim without some evidence, have you found a link to some research? Logic would tell me, how would your eye know, when you saw only a 24 12 or just one photon? The link I found says 24.
     
  16. Aug 8, 2004 #15

    selfAdjoint

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    The research was by some guy at Penn State, decades ago. He used volunteers in darkened rooms with very low controlled photon flow. His original minimum perception was three photons, but when he sharpened up his controls he was able to exhibit response to one photon. I'm sorry I don't have a link but it was very well known research.
     
  17. Aug 10, 2004 #16
    I believe that it was the experiment of Hecht, S., Schlaer,S. and Pirenne, M.H. (1942). It was published in J. Gen. Physiol., 25, 819-840. They concluded that a rod is capable of responding to a single photon.
    I suggest also the following link: http://beagle.colorado.edu/courses/3280/lectures/class14-1.html
     
  18. Aug 10, 2004 #17
    Thanks I been looking for a link like this one. :smile:
     
  19. Aug 10, 2004 #18

    russ_watters

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    It is a very complicated question and that is a very helpful website.

    I don't know when the last time any of you have sat in the front row at a movie, but the same movie that appears smooth when you are sitting far away looks jittery up close: how fast something moves across your field of view matters too.
     
  20. Aug 10, 2004 #19
    OK then, never mind. I'll post something more specifically on topic: Anybody else here start seeing the little cigarette-burn-like spot in the corner of movies only after seeing Natural Born Killers (at least, I THINK it was that, maybe Pulp Fiction. Or something) where one character explains this phenomenon and it's purpose to another?

    I had an editing instructor who could accurately describe a single frame image inserted as a joke into a film running at full speed - 24 FPS. As in "Was that some kind of clown on a subway car?"
     
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