Sunday, April 4, 2010

Pulling Green Screen.

Hello all.



Recently I was given a job to extract people from green screen shots. There are forty different photos, thus I'm trying to stream line this process. I'm not having much luck though. I've used the color range option, but the hair is the real problem because it leaves a greenish halo in the different strands.



I've also done a trick by switching to LAB color mode, duplicating the ''a channel'' %26amp; adjusting the levels until you achieve an extreme contrast %26amp; creating a mask that way. It's worked the best, but it still takes some time %26amp; there is still some green present.



My brother uses After Effects quite a bit because he's in video production. He too uses green screen, but it's so simple to pull in After Effects vs. Photoshop. Does anyone know of any other tricks or tips to really pull the green behind someone. Unfortunately, the green screen doesn't appear to be too evenly lit, so there are different shades of green throughout. The real problem is the hair. Any suggestions would be GREATLY appreciated.



Thanks!
Pulling Green Screen.
PD,



What happens when you expand the range of ''green'' colors selected?



Also, there are several standalone and plug-in software programs that can do hair well. OnOne Software's Mask Pro 4.1 and Tiffen Dfx software come to mind.



Neil
Pulling Green Screen.
PD,



What happens when you expand the range of ''green'' colors selected?



Also, there are several standalone and plug-in software programs that can do hair well. OnOne Software's Mask Pro 4.1 and Tiffen Dfx v2 software come to mind.



Neil

Under Layer%26gt;Matting, there are options for defringing. These will often help your situation. In fact Corel Knockout relies on these to finish their operations. Sometimes it's too much and needs to be backed off a bit or painted in, but that's easy enough to do on a duplicate layer.

Understand also that TRUE chromakey is an integrated hardware/software system, and has some strict set up and calibration requirements in order to produce the best results.



With what you want to do, you can succeed in ditching 99.99999% of the background, and get nice smooth edges, but then you have to worry about objects taking on and reflecting the color of the backdrop they're shot against.

That's where it can get tricky.



I wish I could offer a one-size-fits-all solution, but there isn't one. Good studio shots with expert lighting techniques go a long way toward mitigating the problem in the first place. It's a real art, and not many folks are able to manage it well.

Google for tutorials on ''extract image.''

Phos,

%26gt;you have to worry about objects taking on and reflecting the color of the backdrop they're shot against.



That's a good point. Often times, reflected color (whether from green screen or bright objects that have been masked out) becomes very apparent once the art is silhouetted.



Neil

That is very true. The photos I were given weren't that great. They were RAW files, so that is nice, but they shot it on a green screen that wasn't evenly lit, several of the models had come green hues in their clothing, %26amp; one of the models was even wearing a reflective jacket %26amp; shoes. So, that being said, it's pen tool all the way. I've messed around with Mask Pro before. I thought it was decent. Perhaps I should try it again. But I guess when you're relying on others to photograph the models, you're at the mercy of their training!



Thanks for the advice!

Is defringing a way of contracting the selection or does it have to do with tweaking some halo color remnants? If it's contracting the selection, I either use the feature under modify, or the Minimum feature in filters to reduce my mask by a pixel or two.

Sometimes (around hair strands, for example) a workable fix can just be judicious application of the desaturation brush to kill remaining green.



Neil

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