Green screen

JRey wrote on 9/18/2014, 3:55 AM

Actually I am using blue at the moment and reflecta media. All in all I have quite a good key however I noticed the post about NeatVideo which got me thinking, never a good idea.

If you have a green screen shot with some grain in the green if you applied NeatVideo first in the effects chain then other plugins ending up with chromakey would that improve the end result.

In theory by making the green as flat as possible with NeatVideo should give you a better key or am I way off line here?

Comments

johnmeyer wrote on 9/18/2014, 10:42 AM

I don't do green screens, but I do a LOT of noise reduction. I would think using noise reduction before the key plugin would make the key worse because Neat and other NR plugins work by averaging pixels from adjacent pixel positions (left, right, up, down) as well as from adjacent frames, in order to reduce the noise at each pixel. This might tend to make the edge of the key more noisy, not less, because the averaging from areas outside the blue screen would make it less blue and thus kill the key.

However, perhaps someone else has actually done it and can speak from experience.

JRey wrote on 9/19/2014, 3:39 AM

Thanks for the thoughts John. I have not had the chance to try it yet, but I will at some point.

farss wrote on 9/19/2014, 8:25 AM

Agree with JM. How to get a good key is well covered in numerous tutorials on the Internet. Invest in a good screen and lighting. A roll of CK green paper makes for a good screen.

Have plenty of separation between the screen and the talent, that reduces spill and could help by getting the screen out of focus. A camera that records 4:2:2 will help. Remember the screen has to be big enough to cover the talent and needn't be any bigger, the rest can be taken care of with a garbage matte.

Bob.

musicvid10 wrote on 9/19/2014, 8:42 AM

Lighting, lighting, lighting, in that order.

JRey wrote on 9/19/2014, 12:38 PM

Yes I know and I agree. I am not trying to fix something, just a train of thought in case.

astar wrote on 9/19/2014, 1:06 PM

Shooting as close to uncompressed as you can afford, and better color than 4:2:0 (avc) will get you the best key. Compression like AVCHD adds a fuzzy dither to the key edge, which no amount of post processing will get rid of. Getting some separation between the screen and subject also helps, but also increases your screen size. The distance is meant to eliminate color bounced on to your subject, and not impact your subject lighting.

Garbage matt the sections you do not need, then key the remaining edge that way you screen only has to be flat lit near the key edge.

Green is not the only color to use for keys. For the Deep Space Nine space station shots, they used orange because there was so much blues and greens in the model. Of course tech has progressed substantially since DS-9. Green is generally used because it tends to not interfere with skin tones, unless you are getting bounce from your screen on to the skin tones.