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Chroma Key troubles
OK…lets just say I’m a little new at using a chroma key screen and it’s showing.
I have a series of shots using a green screen, and they are not chroma keying very well. I think the problem is that I don’t have enough light on the screen.
My question for anyone who can help…is there a way to save my butt!
Can I lighten the green only? Can I pick out only the green and change the color so it keys better? Any other suggestions? And yes, next time I’ll light the green a lot better!by the way, I’m using final cut pro HD on a G5 with Cinewave Pro.
Thanks, Randy
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8 Replies
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I think I should be clear in that the shoot is over, and I can’t re-light and try again. The green I have in the background is what I have to work with now…
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How are you taking in the footage? DV? Uncompressed?
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The type of footage you’re using will effect the quality of your key as well as the lighting. DV25 is not that great, DVpro50 is better, BetaSP (for keying) is even better, and Uncompressed will give you the least trouble… as long as it’s lit correctly.
Depending on the type of footage you’re using there are 2 filters you can drop on your footage before the Chroma Key filter; Color Smoothing 4:1:1 and Color Smoothing 4:2:2. Essentially (or at least the way I understand it) those filters smooth out the pixels of your footage so that you can get a better key, easier. As I’m sure you know, the 4:1:1 and 4:2:2 are specific for the footage you captured. Try those and see if it doesn’t improve your key.
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If your footage is really bad, then you can probably save it with DVMattePro – it’s not free, but worth every penny if it’s going to save your butt.
Wayne
2DP G5, 3.5GB RAM, FCP HD
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dvMAtte Pro is an excellent product, and works really well in FCP. It can be downloaded from dvgarage.com and you can try before you buy. In addition, you might also consider a technique that works really well in After Effects – I haven’t tried it in FCP but I imagine it would work equally well. What you do is isolate individual areas with an articulated garbage matte and put each one in it’s own layer – hair, arms in motion, etc., since these things do not always respond the same way to the keying app. That way you can get the absolute best key possible for each problem area and, when assembled, it will look much better than an overall “average” key that is nothing more than a compromise. Bear in mind, again, that I do this in After Effects, but it should work just as well in FCP.
Good Luck.
Arthur VIbert
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Tae,
I’m bringing the mini-dv footage into the system uncompressed.Everyone, Thanks for your imput! Very NICE!
I’ll keeping checking to see if anyone has anything to add…Randy
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Here’s a possibility:
Go ahead and lighten a copy of the shot to get the green screen light enough to work with. Hopefully you can still maintain a proper seperation between the screen and talent. At this point don’t worry too much about the talent looking OK.
Have your software generate a matte from that copy.
Use the generated matte to key out your properly-corrected shot.
Dean Sensui — http://www.HawaiiGoesFishing.com
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In the past I’ve used a selective color correction filter (Eureka!) to “pick” the green color and increase the chroma content(saturation) of the shot just at the particular backing color. Before using the selectice CC, I will do a normal CC to get the levels in the ballpark. Usually a combination of normal CC and selective CC will do the trick. I also use DVMatte for chroma keying an it does a pretty good job.
Tom
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