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Eyes FPS

  1. Feb 18, 2008 #1
    Does anyone have a good explanation of what fields per second our eyes see, and why it is at that? By why I don't mean evolutionary features, I mean optically, such as beyond a certain fps the our biological singular value decomposition does not not amount to much, something physics or mathy.
  2. jcsd
  3. Feb 19, 2008 #2


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    I don't know enough about this for a decent response, but I can tell you that the eyes 'see' a lot faster than the brain can consciously process the visual input. It's a combination of neuronal functioning and brain architecture.
  4. Feb 19, 2008 #3

    Andy Resnick

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    The vision system is not digital, so concepts like "frames per second' don't apply.

    The human eye has various thresholds which generally vary by size of object, and all of the measured data on detection and perceptionhave to be understood to include the retinal processing that occurs in addition to the simple excitation of rods and cones. Also, distracting someone changes their sensitivity limits.

    For temporal flashes of light, ratio of required pulse intensity over background goes up to 22 for a pulse 0.01 seconds in duration (it's 2 for 0.1 seconds).

    For moving objects, it's trickier because we have specialized movement-detection circuits using peripheral vision. Some insects actually have specific detectors for directed motion. I didn't find a reference for a upper velocity threshold, but there is some data on lower thresholds- probably not what you are interested in.
  5. Feb 19, 2008 #4


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    It's a continuous pulse, isn't it?

    Regardless, I guess you could define a hypothetical "FPS" rate by observing the maximum speed an object of a controlled size, luminescence, etc, at a controlled distance could go without registering in any way.

    I heard the USAF did a couple of tests on pilots where they identified planes in 1/240 frames (per second) or something.
  6. Feb 19, 2008 #5
    I don't know a ton but I do know that what is usually measure is not fps but rather the speed at which you start to see movement as non-continous. This is about 60 Hz. Anything giving off light faster than that will apear to be continous. Therefore anything changing withing that region will seem to have a torn image (like computer screens).
    For example if florecent lights were run on your basic 60Hz electricty you would notice them flicker so they are set to flicker at 120Hz. Some birds on the other hand have their threshold set at 100-115 Hz and therefor constantly see florecent lights flicker. I know a little more about the biological process but I am not sure that is what you are looking for.
  7. Feb 19, 2008 #6
    Alright, I'm satisfied with the limitations of the eye at this point, but what exactly is that limits the eye? Brain capacity arguments are too general. What is that the brain is doing to process images?
  8. Feb 20, 2008 #7

    Andy Resnick

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    Well, you should think of the retina as being part of the brain. There are about 7 layers of processing that occur in the retina: local averaging, difference subtraction, etc. etc., in addition to having rods and cones dispersed differently over the retina.

    The eye also accomodates and has saccades; I'm not sure if the purpose of a saccade is known. The image on the retina formed by the optical elements of the eye is highly aberrated as well.

    I wonder if it's more correct to say the eye limits the brain. It's possible to correct vision to 20/10 or better with LASIK techniques, supposedly one is constantly distracted by seeing dust in the air and pixels on a tv.
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