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Keying Problems

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Simon RuschmeyerKeying Problems
by on Feb 22, 2010 at 11:50:29 pm

I got some relatively bad material for keying. The color codes of the yellow suits and the green screen are nearly the same. I tried Keylight but did not come close to a clean key. Any suggestions? Is their a plugin which combines Masks and keys? Or a plugin where I can define the two colors I want to seperate from each other? Any help would be so much appreciated!

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David JohnsonRe: Keying Problems
by on Feb 23, 2010 at 1:20:00 am

Any chance of re-shooting with a bluescreen? Sorry to suggest that, but it really seems the approach that'll be both least time-consuming and still yield decent results since that literally looks like the textbook definition of a chromakey nightmare ... the background doesn't look chroma green at all and, even if you find a way to separate the men's clothes from the background, you'll still have to deal with the areas where the yellow background reflects onto other objects (i.e., each TV in the back row).

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Dean SensuiRe: Keying Problems
by on Feb 23, 2010 at 3:48:22 am

Was your camera set to skew the colors? It appears as though you have the camera set to provide a certain "look".

If so, then that's part of your problem. Any in-camera color adjustments when doing green screen will compromise the chroma information in the shot, and that chroma information is crucial to discern what portions of the image is part of the matte and what's not.

It could be that the green you chose has way too much yellow in it. What was the source of the green screen material?

The green screen might be too hot in some parts. When setting green screen it should ideally read as 50 IRE.

Primatte is actually able to distinguish one green from another, and I've successfully keyed green on green (my fault for not sending a memo). Yellow on green is a breeze. Keylight, on the other hand, isn't nearly as adaptable as Primatte. Keylight tends to sacrifice detail to pull a tighter key. Primatte, on the other hand, relies upon better user definition of what is and isn't green to pull a tighter key.

With Keylight, you tell the program what's green. With Primatte, you tell the program what's green, what's also green, and what's NOT green. That alone makes a huge difference in the results. Then there are a long series of fine-tuning controls that requires the user to carefully read the user manual just to make sure the program is used to its max potential.

Hope this helps.

Dean Sensui -- Hawaii Goes Fishing

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Michael SzalapskiRe: Keying Problems
by on Feb 23, 2010 at 3:54:04 am

What's wrong with that green screen? It's smooth (except for that crease down the middle), but oh wait; I see where you might be having problems; it's not lit evenly. There are obvious areas of light and dark, you've got to make sure you've got clean lighting and OH MY LORD that is nowhere near the right shade of green!

Yikes. Just. Wow. If whoever gave you that footage expects you to do it quickly/cheaply has some chutzpah, that's for sure.

Yeah, there are plugins that combine masks and keys (Keylight, for example) but that's not going to help much here. Those things are the same d*ng color.

My suggestion is to go ahead and do a key for their heads, but you're going to have to rotoscope their bodies. Heh, if your rotoscope's not quite perfect, it may not even be noticeable since it's essentially the same color as the clothing. (Obviously, the TV's will help a lot too. You don't have to animate a mask where the TVs are)

However, the reflectivity of the TVs is going to prove an issue for realism. It's gonna be a huge pain to try to reflect your background on them.

I would suggest you do what David said: have them reshoot it on blue and preferably with someone who knows what they're doing with lighting on set too.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.

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Simon RuschmeyerRe: Keying Problems
by on Feb 24, 2010 at 10:22:18 am

Hey guys,
thanks for your remarks.

No, I can't reshoot with BlueScreen. Im not such an expert in rotoscoping so Im thinking about masking every single frame in Photoshop, should be faster, at least for me.

Thanks again, I really appreciate your help,
Best, Simon

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