keying

if i have something with a black background in premiere, and want to replace that background with something else, like another video, how do I 'key' it to work? I am having major issues with taking an exploding wall, where the black background comes out, and putting a video behind it.

thanks

I don't know what software you are using, but in Premiere and After Effects you can set the transfer mode to "screen" which will overlay anything that isn't black on top of what's underneath.

premiere

The problem with using black for this kind of thing is that it will key out other black elements of the shot that you don't want keyed out. That's why we use chroma key for keying out backgrounds. For digital footage, green usually works best. For film, blue is better. But either will work. You can try using a key based on luminance differences (a "luma key"), or perhaps an RGB difference key.

Yea, csproductions, this is the problem I ran into last night. I figured out how to choose a color to key, but then it made everything that was black in the video transparent.

Here is what I did. I made the video in After effects and it is using the shatter plugin. What I want is the wall to shatter and then the background to be another video. It has to be something with the matte or some function where I need to export the alpha channel matte... Any ideas? I'll upload what I have so far and maybe someone can help better.

Why not just put the AE effect on a green background (layer the wall exploding on top of a green or blue bg, then pre-comp - or render - then use the new clip to key out the green or blue, then layer the new keyed clip over the bg video you want to use.

And to that I say 'PERFECT IDEA'! Thank you!

Just go back to your original shatter project in ae and render it with an alpha channel. For your codec choose "Anim+".