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Tips on effectively keying out wind-blown hair?

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Betsy LandsteinerTips on effectively keying out wind-blown hair?
by on Apr 15, 2013 at 7:03:44 pm

Hey! I'm pretty new to the whole Green Screen world... in fact, this is my first project. I did my best to research and prepare myself with as much knowledge as possible on the topic(the internet is a wonderful place!), but I still ran into a few issues. I "finished" editing this project in After Effects CS6, and noticed some artifacting(I think that's what it's called..), or green screen that didn't key out, especially around my hair(which the wind blows pretty intensely at parts... I'm guessing that's what is causing my problems).

I was wondering if there are any helpful tips/tricks that anyone knows of that would help to eliminate this? I don't have the budget to go buy any special software, or ad-ons.. so unless it's free, I'd prefer learning of things that I could do with After Effects and it's already built-in goodness.

Here are a few images of the project to get an idea of what I'm talking about:

http://bit.ly/XCIqll
http://bit.ly/12fKjWZ
http://bit.ly/138QElT
http://bit.ly/117ER4l

as you may, or may not, be able to tell.. I'm not having a problem with the artifacting on the hair of the "ghosts" behind me. I'm guessing that's because of the opacity difference?



Thanks in advance!


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Jason JantzenRe: Tips on effectively keying out wind-blown hair?
by on Apr 15, 2013 at 8:17:55 pm

Hi there Betsy,

My first guess at fixing the wispy hair, if I were to have a go at it, would be to add a mask around that section that you need to feather and then use that mask feather tool in cs6 (hopefully you're on that). If you are in cs6, there's also a quick fix that's sorta like the new features introduced for the next version of after effects - that rotobrush tool, which is what you would use in Photoshop to extract wispy hair. You could apply the refine matte effect and that will account for motion blur and fine details, but again, it's more of an auto fix. I'd try both of those first, if no satisfactory results, you might have to export the frames to a PNG sequence and edit each frame in Photoshop to get the best alpha channel possible.

You're practically into rotoscoping when you have to get this detailed on a key, so get ready for some work and frame by frame attention :)

Jason Jantzen
vimeo.com/jasonj


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Betsy LandsteinerRe: Tips on effectively keying out wind-blown hair?
by on Apr 15, 2013 at 8:30:48 pm

Jason,

Thank you for your suggestions! I'm actually not looking to completely get rid of the whispy hair... more along the lines of getting rid of the green screen particles that are hanging on and making the edges of my hair look... pixelated? I'm not sure how to describe it... chunky? Haha! I am looking for extra tips and tricks to smooth the edges of the hair out to make it look smoother. Is that even possible?


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Jason JantzenRe: Tips on effectively keying out wind-blown hair?
by on Apr 15, 2013 at 9:19:16 pm

Right, you wouldn't mask out the hair. This might be better done in two steps, first step being tracking her face so that you don't need to keyframe the motion of the mask all over the place. That's very easily done in Mocha. If you don't know to do that, there is a ton of help on the cow for that too. Basically get a good track, then create a solid layer, draw a mask that masks out her hair, so you're left with essentially a scalpless, body less girl - a head with no hair. You're focusing on the hair, and only tracking the head, so you don't need to reveal the whole girl at this point. There's a drop down menu on the keyed out layer for the girl called "TrkMat". Set it to Alpha Matte. This will use the mask you just drew on the white layer as a matte to reveal the layer below it (much like a clipping mask in Photoshop). Make sure the white layer with your mask, which is now an alpha matte, is parented to the tracking null (I usually copy the tracking data from Mocha onto a null object) so that the mask moves with the girl's head. This way you don't actually have to animate the mask, just make a shape that tracks her movement and then sometimes a few minor adjustments to the masks shape here and there. Go through and make sure the matte layer isn't going crazy all over the place. Once you're happy with that, duplicate those two layers. Delete the mask on the duplicated white solid you just made. This will reveal the girls hair, but also the rest of head. This is where the real work begins. You need to draw a mask that reveals only her hair and then begin keyframing that to track her hair and refine the edges of her hair.

Like I said before, you can choose this long drawn out method, which is pretty much rotoscoping her hair to catch all those wisps, or simply try the refine matte effect on the keyed out layer. This will give you some smoother, and more desirable edges - eliminating the chunky bits you're talking about, but often times eliminating too much of the hair to begin with.

To get rid of that green bleed on the right side, you can try working with the spill suppressor (under the Key menu). That effect was specifically created to address what you're talking about. Did you use Keylight? Because there are some tools in there to clean up the edge colors as well as any green light reflection on her skin if any.

Let me know if you need any more help, glad to offer it.

Jason Jantzen
vimeo.com/jasonj


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Betsy LandsteinerRe: Tips on effectively keying out wind-blown hair?
by on Apr 16, 2013 at 7:08:03 pm

Jason,

Thank you for explaining that further. I obviously have issues comprehending written word. Haha! I'll give those two things a try, for sure!


Thanks again! You've been very helpful!


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Darby EdelenRe: Tips on effectively keying out wind-blown hair?
by on Apr 16, 2013 at 12:14:57 am

You may have some chroma subsampling issues that could be partially resolved in After Effects by:

1) Applying the Channel > Channel Combiner effect.
2) Setting this to RGB to YUV.
3) Applying the Blur & Sharpen > Channel Blur and increasing the Green and Blue Blurriness amount (enter the same values, I recommend starting quite low). This blurs the U and V components (the chroma).
4) Apply another Channel > Channel Combiner effect.
5) Set this one to YUV to RGB.

You would do this before the key effect.

Other than that it's difficult to say exactly what the problem might be without seeing the original green screen footage.

Darby Edelen


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Betsy LandsteinerRe: Tips on effectively keying out wind-blown hair?
by on Apr 16, 2013 at 7:10:06 pm

Darby,


Thank you for your response! I will look into those things as well! You've given me a lot of options to try! If it helps to see the original green screen footage I'll put a link below to an image of said footage. Let me know if that gives you any other ideas as to what could be wrong/how to fix it. :) Thanks again!


Image of Green Screen Footage:
http://bit.ly/15duDGv


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