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stubborn black outline artifact on chromakey
I’m always getting a doggone black outline around my subject when keying out a background using a green screen and using a magenta hairlight. I’m using an ancient DSR250 with 4:1:1 compression (not great). Anyway, messing around with all the controls in keylight I can’t get any satisfaction in getting rid of the black outline. Shrinking the matte makes the talent look really unnatural. I tried using Adobe Ultra, which does a great job of keying. The lighting is even, the whole thing keys out fine except for that crummy black outline. Any suggestions?
Thanks,
Lisa -
12 Replies
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try unchecking the ‘unpremultiply’ option.
Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW -
Any suggestions for Primatte?
I have the same issue. When I apply Colour Finesse to a keyed layer, the translucent parts of the matte turn dark, producing a dark halo around hair etc. On an adjustment layer above? No problem, but then it affects the background of course.
Cheers,
Daniel
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I don’t think it has anything to do with what we’re doing in AE or Primatte – the software seems to be just a way to make the best of a bad situation. I think it has more to do with the in camera compression and how it interprets the chroma (or perhaps luma) difference. I’m just wondering if there’s a plug-in out there that deals with just that issue….or maybe a lighting technique, or a setting in the camera I can change (besides sharpening – which doesn’t exist on the 250 anyway).
Like, is there an F-stop difference between the foreground and background that would add up to the compression NOT making this black outline? Jeez, this is really bugging me.
L -
Sorry, I misread the original post. My problem is slightly different. Having shot on DVCPRO HD and supervised the shoot, under the circumstances the footage couldn’t be much better. The key is fine, that is until I apply Colour Finesse at which point the grey parts of the matte turn dark in the key. This is before I have even tweaked any of the settings in CF. Other colour correction filters cause no problems and CF doesn’t either if it is on an adjustment layer, but using an adjustment layer means that all the layers are affected.
Regards,
Daniel
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Thanks Dave, I was trying to avoid pre comping as I would end up with quite a few of them but you got my brain ticking and the way I have things set up already I’m pretty sure I will be able to get away with putting most of them in the one pre comp.
Cheers,
Daniel
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Hi Dave,
don’t have an iPod and when I click on the link you provided, I get a blank screen. But to answer your question, yes, I believe I’m following the established protocol for shooting chromakey. I’m lighting subject and background separately, evenly lit background (even tested it with a light meter), no spill from foreground lights (key and fill on the subject with magenta hair light). So, the only thing I feel like I’m missing in the equation is that perhaps the ratio of light from foreground to background might be too much, or too little?
Lisa -
Hi Kevin,
thanks for the suggestion. I checked (and unchecked) premultiply in Keylight, but all it does is add a sort of grimy-looking black blur around everything. I see that it HAS some effect, just not the one I need.
L -
Dave,
This is very thorough, and I’m very glad to know this information.
The situation here is that I have a background that is a .mov file behind an After Effects animation of Illustrator, Photoshop and .jpg graphics with my subject chromakeyed in front of all that. But I’ve gotten this black outline in front of just still .jpg images before as well.Doggonit.
This is why I have to suspect that it’s something to do with the lighting or maybe just the 4:1:1 compression of the SD footage taken on a DSR-250. When I look at just the footage of the subject on the green background, there IS a black outline around her but it’s only visible on her red sweater against the green, not her flesh tones or her blonde hair against the green. So I think it must have something to do with the way either A) the camera is interpreting the chrominance or B) the saturation of color or C) the luminance difference (or lack of it). That’s why I keep figuring that maybe a change in lighting or F-stop or something might help. Or maybe changing the knee or something.
Lisa
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OK I surrender. I hate it, but I surrender. You know, come to think of it, the last time I had a black outline my talent was also wearing red. Hm. So maybe if my talent this time doesn’t have the black outline on her flesh tones and her blonde hair, I’ll tell my talent to wear peach or yellow on green screen. Well, I guess I’m just dealing with a compression issue. Ugh.
Thanks for your help.
Lisa -
I have been able to ket a good key with both Ultra and Keylight. If you post a link to download a small sample clip, I’ll see what I can do and give you the preset for it.
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