Green Background?

Hi, I am a n00b and crazy about looping videos. I have a question: how do I make the Green Background in some of the videos transparent, or combine it with another video/picture? I really want to know, for my own personal purposes, of course! ;)

You need a video editing program like Adobe Premiere Pro or Final Cut Pro or a graphics/effects program like Adobe After Effects to make the green background transparent.

The green color allows you to chroma key itself out (tell the program to ignore that shade of color and cut it out of the picture, simply put). The reason that shade of green is used is because it's not in any skin tones of people, so no part of their face or body will become transparent.

Here's a link to download a trial version of After Effects CS3. You'll have to register with Adobe first, then you can download the trial.

https://www.adobe.com/cfusion/tdrc/index.cfm?product=after_effects&promoid=DJDUG

Once you install that, go http://www.videocopilot.net/basic/ and do the After Effects Basic Training. Lesson 4 is about keying. That should give a start.

You can also use Sony Vegas 8.x and even a cheap product called Magix (around $70.00) which is a full NLE as well. Just look for Chroma Keying and Alpha channel stuff within the products.

You know, I don't like using greenscreen because you always have to tweak everything and it always seems kind of artificial.

I recently had an idea though... What if you bought a projector and used it to display a background directly from a computer. You could play a clip of a room on a projector (projecting on the screen behind the actor) and you have an instant set! sort of... Maybe the refresh rate would be apparent, it might not work but it would be easier than greenscreen if it did.

Hey Mark,
I have access to a couple of projectors, I had some ideas to use them in a couple of concepts I thought of, but I'll try this too and let you know how it works.
Off hand though, the background there projected on would have to be pure white without any imperfections I would think. I don't have that, but for a test, we'll see.

Jake

won't work nicely with projectors. The reason is depth of field. Focus on the subject, then the background defocuses. Open the aper, then the lightning will get all screwed up. Most people make a big mistake when doing chroma key work. They stand too close to the backdrop green screen. As long as you are far awy enough from the green screen and focus on the subject, you will get clean keying and it won't look artificial.

Actually, the projector idea is a technique that's been around for a while. There have been a lot of films in the early days before green screen existed that involved rear projecting screens (Hitchcock evidently used this a lot).

Vadervideo brings up a good point about depth of field issues. There are a lot of precise technical precautions you'll need to take. Most notably is the loss in contrast of a projected screen compared to a normally lit set. I believe there are specific materials that prevent this contrast from becoming a problem. This shouldn't stop you though, there are plenty of ways around difficulties if you're determined to work something out, like stopping down for a larger DOF (Besides, who doesn't love a nice and shallow focus?)

If you're into cinematography, there's a huge section on it in the American Cinematographer's Manual. They also used it in Science Of Sleep for the swimming-dream-sequence.

Nate