Green Screen (Chroma) Help

drewU2 wrote on 1/27/2010, 9:41 AM
Hello, I have created a studio for a small non-profit and we are trying to get the green screen to work. The problem is that when I choose "pure green" in the chroma effect, some parts of the person I filmed become transparent.

A couple questions:
1) Do I need to have more light on the person in front of the green screen?
2) SHould they wear lighter clothes?
3) any tips using green screen is very appreciated?

Comments

Jay Gladwell wrote on 1/27/2010, 9:51 AM

Drew, have you tried doing a search here or online? There have been mountains of material written and discussed on this subject.


RedEyeRob wrote on 1/27/2010, 9:53 AM

Green Screen/Chroma Keying is an art. For starters check out this vegas tutorial which is relatively basic but will help you.

http://www.sundancemediagroup.com/articles/chromablur_by_kolbo.htm

Also check out this link. This guy has some pretty good tips for getting a better key from inperfect source footage.

http://www.moonpro.us/chroma.htm

Also I have had success using the secondary color filter at the end of my effects chais as a choke to clean up the green aura around the edge of the subject.
drewU2 wrote on 1/27/2010, 10:06 AM
Unbelievable! I just checked out the first link you posted and saw more options on the chroma keyer that I missed on my screen! That made all the difference! The high threshold was hidden in the effects box on my screen so it was set at the top the whole time, and all I had to do was lower it a bit. Amazing.

I really want to that you Rob for your time. You just saved me hours. THANK YOU!
larry-peter wrote on 1/27/2010, 10:12 AM
Agree with Rob, it's an art. Done a lot of GS keying with other systems. With the few times I've tried Vegas' stock keyer with 4:1:1 or 4:2:0 footage I've never been able to achieve better than a "weatherman" grade key even with the tips I've seen. MIght just be me, though. If you're working with a lot of greenscreen video below 4:2:2 sampling you may want to take a look at either After Effect's Keylight or Digital Fusion's Ultra Keyer. They have excellent blur, matte choke and spill controls built in.
RedEyeRob wrote on 1/27/2010, 2:45 PM
When tweaked a decent key is possible in Vegas. Here is a pretty good Key I pulled from Vegas with just a cloth backround purchased at the fabric store taped on the wall in the hallway of a school and no lights at all. Just the existing hall lights.

Original
http://i950.photobucket.com/albums/ad343/imagecraft/Image9.jpg

Key
http://i950.photobucket.com/albums/ad343/imagecraft/Image8.jpg
richard-amirault wrote on 1/28/2010, 5:28 AM
Here is a pretty good Key I pulled from Vegas with just a cloth backround purchased at the fabric store taped on the wall in the hallway of a school and no lights at all. Just the existing hall lights.

Nice, but in this case (no lights) you have the advantage of *even* lighting (the existing hall lights) Often it is hard to get the green screen evenly lit .. and that is a *very* important step in the process.
Edward wrote on 1/28/2010, 7:36 AM
Some quick tips:
- avoid white & yellow, it reflects green (if you have a wall and floor painted)
- use a back light to shine on top of shoulders and head to create separation
- make sure lighting on green is even. any hotspots will give you a headache in post.
- lighting on green should be SEPARATE from lighting on subject.