Difference between revisions of "Film Projects"
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* Y: [http://en.wikipedia.org/wiki/Luma_(video) Luma] - Brightness black-and-white signal | * Y: [http://en.wikipedia.org/wiki/Luma_(video) Luma] - Brightness black-and-white signal | ||
* UV: [http://en.wikipedia.org/wiki/Chrominance Chrominance] (blue and red components) - Color signal | * UV: [http://en.wikipedia.org/wiki/Chrominance Chrominance] (blue and red components) - Color signal | ||
YUV is not an absolute color spacem, it's a way of encoding RGB information [http://en.wikipedia.org/wiki/YUV#Luminance.2Fchrominance_systems_in_general]. | |||
'''Chroma resolution [http://en.wikipedia.org/wiki/YUV#Luminance.2Fchrominance_systems_in_general]:''' | '''Chroma resolution [http://en.wikipedia.org/wiki/YUV#Luminance.2Fchrominance_systems_in_general]:''' | ||
Revision as of 15:27, 6 April 2008
Blue or Greenscreen
Aka. chroma key, and color keying.
YUV color space [1]:
- Y: Luma - Brightness black-and-white signal
- UV: Chrominance (blue and red components) - Color signal
YUV is not an absolute color spacem, it's a way of encoding RGB information [2].
Chroma resolution [3]:
- 4:4:4 (Y:U:V) - full resolution / high bandwidth
- 4:2:0 (Y:U:V) - less color resolution / lower bandwidth
- 4:1:1 (Y:U:V) - less color resolution / lower bandwidth
MacBreak part 2 explains and shows how chroma subsampling works.
The green information is usually preserved in the Y channel [4]. Which makes a green background perfect because of the extra channel resolution on 4:2:0 and 4:1:1 based cameras. In addition green is not a color usually found on a human being, making it easy to key.
Quotes:
If you can plan your DV shot to have mostly dark subjects (dark hair & clothing) in front of a green screen (or bright/blond subjects in front of blue), you can use the color difference key to pull a quick core matte, then turn to a luma-based solution to bring out the edge details.
With DV and DVCam, you won't have as much color information per pixel due to compression, so good mattes are harder to pull. It ends up looking pretty aliased. Both NTSC and Pal DV formats have pretty low sampling (4:1:1 for NTSC and 4:2:0 for Pal).
It was all pixelated and jagged edges. How do u get around this? The technique that I've heard used most often is that you blur the UV channels (the chromanance part of the YUV) then mix that back in with the Y (luminance) and your ready to pull a matte. Do just enough blur so the pixelated jagged edges soften. Use that only for pulling the matte. Once you've got your matte, go back and use the original footage for applying the matte.
- CGTalk GreenScreen
- PCQuest Matte creation in After Effects
- dvGarage dv Matte Pro
- DVCreators Green Screen!
- MacRumors Bluescreen on the cheap?
- Bluescreen on a budget
- Tips for compositing DVC Pro HD footage
- Making Light Of The Matter
- MacBreak HD green screen shooting part 1 - setup
- MacBreak HD green screen shooting part 2 - resolutions and color compression
- Wikipedia Chroma subsampling
- Chroma key Wikiepedia Chroma key (Bluescreen)
Programs / Plug-ins
- dvMattePro
- Keylight
- Shake (OS X only)
- Final Cut Pro (OS X only)
