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24p and green screen


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#1 parklandmedia

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Posted 17 May 2006 - 01:54 PM

Hey there,

I have a Canon XL2 and I am shooting a TV show about super heros and wanted to know some things about 24p

I would like to shoot the show in 16:9 24p. We will be doing some green screening and I was wondering will the 24p casue any problems when I go to chroma key. Someone told me you will get lots of bluring if you use 24p and a green screen. But I have not found anything about this problem online.

Would it be better to shoot in 24p, 30p or 60i?

The reason I want to use 24p is mainly becasue of the look and feel of it. It makes me tear up every time i see it. The super-hero part of the show needs to be very different from the other parts. So I want to use 16:9 + 24p + the CINE setting.

any ideas?
Steve
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#2 David Mullen ASC

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Posted 17 May 2006 - 05:25 PM

The 24P shouldn't cause any keying problems, unless you shoot with a 1/24 shutter instead of 1/48 or 1/60 -- 1/24th of a second shutter speed might generate a lot of motion blur for fast moving objects.

Certainly 60i is no better than 24P since you've got interlaced fields to deal with. You may want to first extract the true 24 frames from the pulldown recording before compositing, rather than try and key 24P-to-60i footage with a 3:2 pulldown.
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#3 Jaan Shenberger

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Posted 17 May 2006 - 10:52 PM

as a general rule, progressive footage is a lot easier to deal with when keying, in addition to making it less complicated when performing transforms (rotations, scaling, etc.) when you mix the shot into the final composited shot.

as david mentioned, make sure you remove the pulldown for 24p footage, whether upon capture or when you import the footage into the compositing software (most have this option).

if you've never shot dv25 for greensceen before, you're gonna have some challenges pulling a good greenscreen matte, though. there's lots of info online describing various recipes and techniques to optimize the key, so it might be a good idea to look them up before the shoot.

hope this helps.
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#4 will

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Posted 29 May 2006 - 01:44 PM

capture uncompressed using s-video and light correctly, then use keylight in After Effects.

if this will be shot in one location do you have access to an uncompressed capture system?
if you have a Final Cut Pro setup with a AJA IO or similar just make a new capture preset
for anamorphic 60i and capture s-video at uncompressed 8 or 10bit or even JPEG 75-100%.
Remove the advanced pulldown in After Effects and voila! 25-50% more color information,
even through the s-video.

Your camera settings should be 16x9 and using advanced pulldown (2:3:3:2). We captured
audio to the camera and synced with a slate to the external video.... which is like the opposite
method that most people do.

IT IS A COMLETELY DIFFERENT CAMERA!!

Make sure your scene is lit to the capture window of FCP or hook up a good CRT to the
component or Svideo out of the IO. It records about 1-2 full stops darker than DV capture.

Just tried this about 2 months ago and was so amazed with the quality differnence that we
shot two studio commercials using this method.

Still a great SD camera in my opinion!

will griffith
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