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superjab
02-17-2005, 03:18 PM
Hi guys, i have a question for you.
I would like to know how people can make film with real actors with green screen in background and then in post-production substitute the background screen with a digital landscape, a matte painting or whatever.
Thanks very much.
I guess it could be done with after effects, is anyone know how to do it??
take care.

superjab

DesireeJReynolds
02-21-2005, 09:44 PM
Ok, I am not the expert on this, but I have done it once or twice for post production of a TV commerical. It can be done in Adobe Premeire, and its called "keying out" This feature is found in the same menu where all of the other keyframe effects are... (cant think of the name of it, as its been awhile... I dont work at the TV station anymore....) Anyway, just play around you'll find it... this feature will take out everything that is that particular shade of green (or blue depending on your screen color) and leave the area around your subject transparent so whatever you have on the layer below your subject shows through... Be very careful with how you light your subjects in front of the green screen. It is very difficult as it is, keep your keyouts "clean"--many times there is a green glow around the edges of your actors because of the reflection off their bodies... it can be very hard to get rid of!

Hope that sort of helps:)

Fungusmonkey
02-22-2005, 12:12 AM
Also, here's the guerilla tactics for blue/green screening (I've done this a few times on personal projects):

1. Build a large frame out of wood or pipe, and wrap a bed sheet tightly around it.
2. Pick up green or blue paint at any hardware store, making sure to pick as bright and as "true" of a blue or green as you can. Matte finish will absorb more light, so that it doesn't bounce off and cause you lighting problems.
3. After applying a few coats of paint, the sheet will sag slightly, so you'll want to stretch it tight again and pin or staple it down to the frame.
4. Film your actors or objects, taking care to cautiously light them. (TIP: Film your actors as far from the screen as you can to avoid color-bleed from the screen. I also tend to use a colored rim light on the subject to pull it away from the background more. If you're using green screen, use a reddish light, if you're using blue, use an orange or yellowish light. You can always color correct your subject later.)
5. Take the footage into After Effects, Premiere, Final Cut Pro, Shake, etc. and using their chroma-keying filters to remove the green or blue. Most of the time you can also adjust the filter to remove color-bleeding from the edges if you didn't follow step 4 right.
6. Composite the newly isolated footage, and voila! There you go. Hope this helps a little!

grundelboy
03-02-2005, 05:54 PM
Also if you are going to do any full body shots on the screen you'll want to build a smooth arced ramp leading from the screen to the floor also part of the floor painted ramp and all the same color so you can key out the feet.
( the ramp is for a smooth lighting transistion so you can key out the blue/green color better.)

bdeda
03-02-2005, 10:43 PM
Is anyone familiar with how professional studios compose the sets for blue/green screen? I had thought that they used a particular (semi-reflective) fabric, but haven't been able to find anything refering to the process. Is it really as simple as a "paint and light" answer to this technique?

maop
03-17-2005, 03:32 AM
if you are really interested in getting the 'official' color tone for green or blue screens, go to www.rosco.com, they have a certain tone which is supposed to help you obtain better keys.

In my experience, a good well-lit green matte cloth will do the trick, since AE (and other software) will let you pick your particular tone of green. Just make sure the color is close to the tone you'll find at the website.

You might also buy rolls of greenscreen or bluescreen cloth which allegedly have certain chemicals to make your life easier in post, but they cost lot$ of money.

Maop

MadMax
03-25-2005, 12:29 AM
You might also buy rolls of greenscreen or bluescreen cloth which allegedly have certain chemicals to make your life easier in post, but they cost lot$ of money.

Uh, no, they don't cost a lot of money.

Search eBay, use the work chromakey. you can get varying sizes from tiny little screens up to huge 12' x 30' rolls.

scrimski
03-26-2005, 05:43 PM
Do not use DV, miniDV or DVCPro footage, they produce artefacts due to their compression. Try using Beta SP or DigiBeta, it's a bit more expensive but it's worth it's money.
For more infos about keying (in After Effects) look here (http://www.creativecow.net/show.php?forumid=2&page=/articles/script_gen/clustersort/chromakeying_tutorial_script.html) .

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