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removing background maintaining character
Hi
I am superimposing footage of a circus trapeze artist against film of stars at night to give the impression the circus artist is ‘flying through the stars.’The film of circus artist was shot inside a church building which is the circus school.
How do I remove all the interior background of the church building leaving just the circus artist, so I can then JUST SUPERIMPOSE the artist against the stars at night footage?
Help much appreciatedps Using Avid Med Composer: Mac OS X: 10.5.6
Thanks
Graeme Benson -
5 Replies
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This is a huge question with tons of variables. You are talking about compositing which is not the strong point of any edit system.
Basically, you have two options.
The first is to “Key Out” the material you don’t want. This can be done by selecting the luminance or chroma that you want to remove. This works if the subject is shot against a green screen or a very dark background. The trick here is that you need to have separation between the background levels of luminance or chroma, and the foreground subject. From the sound of it, you don’t have this luxury.
The second option is to erase the material other than your subject. To do this you will probably need to use a process called “Rotoscoping” which means you outline what you want to keep frame by frame. This is a tedious process and requires patience and skill. Also, doing it in an edit system is far from ideal. There are third party programs that are designed to make this process easier.
Usually some combination of the above two processes will be used to get to the desired result in a case like yours.
My recommendation is that you find someone who does this for a living and get them to isolate the shot for you.
Terence Curren
http://www.alphadogs.tv
http://www.digitalservicestation.com
Burbank,Ca -
After you shoot the trapeze artist over a keyable source, you can use spectramatte to key out the background. You will have best luck with well-lit ultimatte green but blue is still widely used.
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If you have a locked-off shot, with and without the trapeze artist, you can use the Boris RT Composite effect, (Apply mode should be DIFFERENCE ) which will make a matte of the difference between the two shots.
There was a tutorial a while ago either here on Creative Cow or on the Avid site.It’s fiddly, but it works.
Juris
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Found the appropriate tutorial,
https://library.creativecow.net/articles/saleh_ra-ey/difference_matte.php
It does depend on the shot being locked off, is fiddly, but works well.
Juris
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Thanks Juris, always good to hear!
Ra-ey
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