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Old July 16th, 2010, 01:39 PM   #1
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Greenscreen 720p vs. 1080p

Hi!

I am using EX1 for greenscreen shots. If the final video will be 720p is it better to shot 1080p or 720p and then scale in post?

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Old July 17th, 2010, 03:09 AM   #2
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1080p will give you the ability to scale up the subject if needed. I tend to always shoot 1080p for chromakey, even for video destined for web projects.
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Old July 17th, 2010, 03:13 AM   #3
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Generally a larger picture will produce cleaner edges. The problem will be downscaling and keeping that quality.
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Old July 17th, 2010, 08:21 AM   #4
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I think I would take the time to do a TEST with my setup, subject matter, and workflow to determine what really worked best for a particular project.

Better safe than sorry...
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Old July 18th, 2010, 04:38 AM   #5
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If your end video is going to be shown in a 4:2:2 environment, shooting at 1080p and downscaling to 720p will, in theory, get you better colour resolution as you'd have been shooting at 4:2:0 but by shrinking those big blocky colour pixels, you're getting close-as-makes-little-difference to 4:2:2.

Having said that, by using a chromakeyer that also uses luminance info to get a better key (in my case, DVmatte Pro), I'm happy with the results from 720p - which has less pixels but the same bandwidth and in my experience has less issues with fast motion. It's also much quicker to work with.

As an example, here's a quick 'mood board' for a recent job that (from about halfway through) demonstrates fairly quick and dirty (no light wrap, no proper colour correction) keys from 720p footage:
(I wouldn't subject you to the full 15 minute version!). Another 'Quick & Dirty' (two days in post) 100% chromakey job - all 720p: YouTube - West Midlands People & Leadership Team

I did do a project way back that was all 1080p, and quite frankly, once it got to delivery, I preferred the 720p results, and have pretty much stuck with 720p ever since. But I think DVmatte Pro has made a huge difference due to its use of luminance info to make the key: dvGarage - dvMatte Pro
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Old July 18th, 2010, 03:14 PM   #6
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Could it not be better to record in 720-50P than 1080 -50i or 25P. Less blurrry edges and better keying.
Havent tried it but it should be considered.
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Old July 18th, 2010, 10:58 PM   #7
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Do a search of this forum. I posted some samples and descriptions of what was done for my greenscreen shots.
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Old July 20th, 2010, 09:24 AM   #8
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Quote:
Originally Posted by Bo Skelmose View Post
Could it not be better to record in 720-50P than 1080 -50i or 25P. Less blurrry edges and better keying.
Havent tried it but it should be considered.
Never use interlace for keying with a 4:2:0 codec IMHO. Having alternating missing lines when you need close pixels to compensate for the missing color information is a bad idea.

Also keep in mind that "motion blur" of lower frame rates can also result in problems when clean edges are needed. Of course faster shutters speeds can help that a bit.
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