Combine two clips into one

Question

Hi, is it possible to take two clips and join them together (that were never joined before, but are two different clips)? I want to make it so both clip appear when viewed. For example, if I had a video clip of it raining outside and a clip of somebody dancing, I would want both clips to be joined into one which would be viewed as somebody dancing in the rain. I am not sure if this is possible, but any thoughts or tips would be appreciated.
Note: (I do know that there is an effect for rain)
Thank you!
-Jason

Answer 1

Jason,
the effect you are looking for is called 'blue-' or 'green-screening'. The name derives from the background color you shoot one scene with. It is was usually blue because it is a color that does not appear naturally on an actor, and can easily be targeted by the composition hardware (a so-called 'chroma-keyer'. Blue worked well because at that time a simple high-pass filter on the blue channel could be used to trigger the composition circuit, and allowed real-time composition on analog hardware).
It basically works like this:
1. Set up a really good lit stage with a blue or green background. It is very important that both background and actor are well lit.
2. Film your scene
3. Film the scene you want to place your actor in (e.g. rain) - let's call it the 'actless' scene because no acting happens
4. Use a chroma keying plug-in ('blue-screen', 'green-screen') to replace anything blue or green in your acted scene with the actless scene.
If you have both scenes shot already (without a uniformly colored background), this will not work.
We do have chroma-keying plug-ins (see here:
http://www.imovieplugins.com/plugs/chromamovie.html
and here: http://www.imovieplugins.com/plugs/chromastatic.html), but currently (while Apple is transitioning to Intel) they have become unreliable. Some of our esteemed competitors have similar plug-ins you might want to look at.
Hope this helps,
-ch
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