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Thread: Framerate in Digital Cameras.

  1. #1 Framerate in Digital Cameras. 
    Forum Ph.D. stander-j's Avatar
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    How does framerate work in Digital Cameras?

    I was thinking about it, and Digital video recording captures motion in a sort of continuous way doesn't it?

    What I mean by that is a video casette is a collection of images on individual frames, right? So the framerate of video camera, that records in analogue, is relative to the speed the film has images being captured on it.

    Digital on otherhand works on memory right? So it's recording X amount of moments or 'frames' in a second, despite that you could potentially record as many as 1 million frames per second - because the image it is receiving is continuous, and because the framerate is dependendant on how much can be stored rather the speed of how quickly a roll a film can spin. Am I right in thinking this, or am I way off on how it works?


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    Comet Dust Collector Moderator
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    Well sort of. You have to collect enough photons to create the image; then you have to download the charges into memory. Neither is instantaneous.

    If you did a million frames a second (if the above steps were possible.) you'd fill the memory in a few seconds.

    For convience in replay, manufacturers generally settle on the same 720p, 1080p, or 1080i frame rate that HD television is projected in, which is far faster than the human eye-brain system can perceive.

    Of course, older devices still use the 525 lines/60 Hz frame rate (NTSC) or 625/50 PAL (and SECAM) systems that SD TV uses.


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    Forum Ph.D. stander-j's Avatar
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    Many thank-yous.
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    Quote Originally Posted by stander-j View Post
    ...you could potentially record as many as 1 million frames per second - because the image it is receiving is continuous, and because the framerate is dependent on how much can be stored rather the speed of how quickly a roll a film can spin.
    Actually the current record for high speed cameras, I believe, is a Japanese contraption that records 4.4 trillion images per second!

    But generally anything over 250 frames per second is considered “high-speed” according to Wikipedia, and the Mythbusters TV show used some much faster than that to capture some truly amazing explosions in slo-mo. With ultra-high speed cameras I believe the heat generated is more of a limitation than memory capacity.
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    4.4 trillion fps is amazing. But when I looked around, it appears that the speed is obtained with a 450x450 pixel image. I couldn't find the bit depth, but I would guess 12, possibly 24, bits depth. Cuts the size of the image significantly compared to the high-resolution we are all accustomed to. But that doesn't deprecate the amazing speed.

    There was a time when 250 fps would accurately be considered high speed, but I doubt that is currently meaningful. Hell, televisions now are mostly 120 fps capable (some say 240, but they are lying).

    I doubt that heat would be a significant factor in cameras, but it would probably kill an iPhone in a few seconds.
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