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Resolution, aliasing and frequencies (inspired by Arri white paper)

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  • Resolution, aliasing and frequencies (inspired by Arri white paper)

    The other day someone posted a link to the Arri white paper (don't remember exact url, but I found it also here: http://www.efilm.com/publish/2008/05/19/4K%20plus.pdf ).

    It has some important implications for BMCC that I'd like to share:

    1. It's interesting to find scientific confirmation that, in terms of the information that is captured by BMCC sensor, it is equivalent to s16 format. The same amount of the smallest recognizable dots / pixels.

    2. A lot has been said so far about how RAW helps stretch DR. But the fact that BMCC captures 2.5K RAW has huge implications for anti-aliasing as well. Before downsampling RAW footage to 2K/HD, it is absolutely important to suppress those frequencies that are prone to produce moire (aliasing) in 2K/HD, and only after that downsampling should be made.

    Here arise 2 questions: does Resolve do this suppression when outputting RAW to 2k? Does BMCC suppress these frequencies when downsampling the captured footage to ProRes?

    In Photoshop this suppression is done using the High Pass Filter, for instance.

    3. It's interesting to analyze some nice and not-so-nice Canon EF lenses' MTF and see, considering the crop factor, which ones are fine for BMC sensor. Should interest be, I can do that in some time.

    PS Beer is like low-pass filter in our lives. General outline of things we do, does not change, but fine movements are "blurred" )) Just funny thinking...

  • #2
    The crucial time to suppress those frequencies is before they hit the sensor in the first place. Once they're in the image, they're in there. You can't just extricate them easily. A properly-engineered OLPF is a vital and necessary component of a properly-designed video sensor system.

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    • #3
      http://bmcuser.com/showthread.php?11...ng-for-the-WIN!

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