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Distort- Aspect Ratio Math

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Lara Johnston
Distort- Aspect Ratio Math
on Jan 24, 2011 at 4:21:49 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 (960x720) into an NTSC timeline (720 x 480) Scale = 75 = 720x960, 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


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Jeff Greenberg
Re: Distort- Aspect Ratio Math
on Jan 24, 2011 at 4:29:56 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

Apple Master Trainer
Avid Cert. Instructor DS/MC
Avid & Color Videos Vasst.com
Compressor Essentials Lynda.com


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Lara Johnston
Re: Distort- Aspect Ratio Math
on Jan 24, 2011 at 4:43:02 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 (960x720) 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


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Olin Padilla
Re: Distort- Aspect Ratio Math
on Jan 25, 2011 at 7:37:26 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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