• Compression Techniques

  Distort- Aspect Ratio Math

  Posted by Lara Johnston on January 24, 2011 at 4:21 pm

  Hi: I am trying to figure out the math for the various Distort/Scale Values entered when resizing footage of various formats to put into various timelines. I understand where the Scale value comes from (say putting DVCPRO HD 720p60 (960×720) into an NTSC timeline (720 x 480) Scale = 75 = 720×960, expressed as a percentage is 75%. But the distort needed, -50, can anyone explain where that comes from and how that number can be explained mathematically?

  I have done a lot of combing through various posts but can’t seem to find that information. If I am missing it, can you point me towards the thread?

  Thanks,
  Lara Johnston

  Olin Padilla replied 15 years, 3 months ago 3 Members · 3 Replies
• 3 Replies

• 

  Jeff Greenberg

  January 24, 2011 at 4:29 pm

  Lara,

  Basically, it’s taking into account for the pixel aspect ratio.
  NTSC .9
  NTSC widescreen 1.2
  DVCPro 720 1.33

  Best,

  Jeff G

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• 

  Lara Johnston

  January 24, 2011 at 4:43 pm

  I think I grasp that concept, but what I can’t seem to get is why the numbers -12.5, -33 and -50 work in the distort tab of FCP pro.

  For example if I cut a DVCPRO HD 720p60 (960×720) clip into an NTSC timeline the aspect ratio requires a distortion of -50 to appear correct (scale at .75 or 75%). How does -50 get derived from the above numbers? Am I missing something?
  Thanks,
  Lara Johnston
• 

  Olin Padilla

  January 25, 2011 at 7:37 pm

  Yeah, this is one of those cases where FCP’s sense of logic makes no sense, so I think most of us just avoid manually setting the distort.

  It’s usually easier to set your resolution manually and ‘conform to sequence.’

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