Video frequency response (modulation transfer function)

Discussion in 'Archived Threads 2001-2004' started by Frank, Jul 18, 2001.

  1. Frank

    Frank Stunt Coordinator

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    I never see any discussions of this key element of video reproduction.
    I understand that the main difference between the look of film and the look of video is the MTF.
    Evidently, the frequency response of video is pretty flat and the MTF of films falls off pretty rapidly.
    Look at graph 6.5 on this website.
    The 35MM release print response drops to zero at 50 cycles per millimeter. That would correspond to 50*2*21 or 2100 lines of resolution.
    That's not much better then 1080 HDTV at 1920. Notice how much the response has dropped along the way.
    The telecine machine that transfers the film to video also has a slopping MTF.
    What about your display system?
    The typical consumer display also has a slopping MTF response, probably quite severe, thus limiting the effective viewable resolution.
    Why is such a key element of video reproduction so little known but virtually every element of audio reproduction is discussed endlessly?
    If I ask what the MTF of a display device such as a HDTV is the answer I get is....well you get the picture.
    My point is that resolution numbers are meaningless without a coresponding MTF (contrast) spec.
    It's like giving a audio freqency response spec without a DB rating.
    Frank
     
  2. Frank

    Frank Stunt Coordinator

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  3. Grant B

    Grant B Producer

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    Many years ago when i was a Ham, I started fooling around with Slow Scan Television.
    I learned enough about it back then to know I don't know squat about it. I think most people are in the level below squat.
    And by analogy, when you say how fast a car goes by a giving a measurement in miles....and nobody even yells about the forgotten "per hours" part, you confirmed it.
     

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