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Is there any hope for this greenscreen? Any methods I can do to fix the "static fringe"?

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Jeff Rouric
Is there any hope for this greenscreen? Any methods I can do to fix the "static fringe"?
on Aug 5, 2013 at 12:05:25 am

A client of mine shot these slow-mo greenscreen portraits without much preparation. Can't reshoot. My job is to key em out and other things, but the problem here is in the keying. I tried a few tricks like making the green greener, and extracting the keylight matte, and that's making it look MUCH better, but there's still the problem of the static fringe that's happening on the low left where I move my cursor.

Seeing the video, and the image of the original footage, could you tell me why this is happening? Is there any way to fix it? It doesn't have to be an ultrarealistic key....just don't want that pixely fringe.

Thanks

Video:





Image : http://i.imgur.com/IlCLBCz.png

In CS6


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Joseph W. Bourke
Re: Is there any hope for this greenscreen? Any methods I can do to fix the "static fringe"?
on Aug 5, 2013 at 12:20:05 am

I think that there's enough contrast in the lower part of your shot that you could successfully use the RotoBrush and get a squeaky clean result. If you do from the neck down with the RotoBrush (if you've never used it, you have to do a couple of tutorials - it's not at all intuitive) on a separate copy of the clip, then combine it with the keyed version, you should be ok.

This should get you moving - it won't take long to get it:

https://www.video2brain.com/en/lessons/isolating-a-subject-with-roto-brush

Joe Bourke
Owner/Creative Director
Bourke Media
http://www.bourkemedia.com


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Jeff Rouric
Re: Is there any hope for this greenscreen? Any methods I can do to fix the "static fringe"?
on Aug 5, 2013 at 12:28:31 am

Thanks Joe, I've seen the RotoBrush tutorials before, I just figured it'd take longer (processing-wise) than just greenscreening it. In the future though, how should my client shoot greenscreen next time? I know about the "well-lit" no shadows, as little variance of green as possible, light set up, but what about distance? Should the subject be closer or further away from the screen?

I mean...there's people in this project that are WEARING green. That is going to be a nightmare.

And are there are pre-cautions to take when shooting greenscreen in slo-mo? It looks to me like the light is flickering, maybe the shutter, which is making this harder than it should be in real-time. Any basis to that?


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Joseph W. Bourke
Re: Is there any hope for this greenscreen? Any methods I can do to fix the "static fringe"?
on Aug 5, 2013 at 3:51:13 am

The subject should be further away from the screen, mainly to allow for two separate lighting setups, one for the greenscreen, one for the talent. Here's a pretty good tutorial on greenscreen setup:

http://lowel.com/edu/lesson_green_screen.html

Anyone wearing green on a greenscreen shoot should be immediately sent for a change of clothing! Actually, the producer should be responsible for letting the talent know this in advance - as simple as an email. Sounds as if someone dropped the ball. But...if there's a good reason for the talent to be wearing green, then shoot against a bluescreen. You can do a mask to keep the green clothing in the shot, but it's work which you shouldn't have to be doing.

In shooting greenscreen, the rule is to use the highest quality camera you can get for the job, ideally one which shoots in at least 4:2:2 - for a better explanation than I can give, look at this:
http://provideocoalition.com/alindsay/story/greenscreen_primer_part_2/

Joe Bourke
Owner/Creative Director
Bourke Media
http://www.bourkemedia.com


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Matthew Woods
Re: Is there any hope for this greenscreen? Any methods I can do to fix the "static fringe"?
on Aug 5, 2013 at 8:48:40 pm

That wobbly surface tension edge of the frame looks to me to be overly aggressive keylight matte cleanup. The shrink/expand matte options in keylight often do this sort of thing. Best to try to get the best key you can before using those cleanup options. You can try adjusting the color that you are keying. Sometimes it works better to just move it manually around the color picker and try to find a color that gives you the best key rather than try to sample it. For poor greenscreens, I sometimes ditch keylight altogether. I personally hate the rotobrush. I find it takes forever, and it often has bad chatter. I prefer traditional rotoscoping over using it. If you can find a setting that will give you a good edge, but has holes in the figure, you could animate a garbage matte to fill those holes.

Here are alternative tricks I've come up with for pulling tough keys. Sometimes they work.

1: Try Premiere. I have enormous respect for Premiere's Ultra Key. It often pulls miraculous keys that I wouldn't think possible. Doesn't always work. Keylight gives you more options, but some footage keys better in keylight, some in ultra key. I wish the Adobe team would include Ultra Key in AE as an alternative keyer.

2: Try the paint bucket effect. I have sometimes had good results with the paint bucket effect applied to an unused corner of the badly lit greenscreen. Sometimes you need several instances of the effect in different corners. When this works, its fantastic. You can even do everything with one effect, check Invert Fill, and set the blending mode to stencil alpha. This trick works well for people shot on black or white which don't key out well with keylight which assumes a colored screen.

3: Try multiple instances of keylight sampling different greens from different sections of the poorly lit screen. Use less aggressive matte cleanup on your keylight, and set the view setting to "intermediate" on early instances to avoid color correcting the greens that you are wanting to key out.

4: If the camera is locked, and you have a clean frame with the actor not in the shot, (or if you can make such a frame). Sometimes a difference matte works.

5: I have sometimes gotten good keys by duplicating the layer, and applying shift channels to the top layer. I set all the channels to full on, then cycle the alpha channel through the different channels till I find the one with the most contrast. I then use the levels effect (on the alpha channel) to increase that contrast. I then use that as a track matte for my color layer.

Just some things to try. I hope one of them helps.

-Matt

Need a quick break from motion graphics?
Try my game Constellation at:
http://www.paperdragongames.com


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Jeff Rouric
Re: Is there any hope for this greenscreen? Any methods I can do to fix the "static fringe"?
on Aug 7, 2013 at 2:21:53 am

Hey thanks Matt and Joe,

Joe, I don't know what the color profile of these clips are, I do know they're MTS straight from the camera (I don't know the camera) though, if that tells you anything.

Matt, thanks for those methods. I've never heard of most of them and I'll try em out.

I'm finding a lot of help from the refine matte filter, which seems to quickly smooth out the edge pixels that are giving trouble...they're still moving a bit, but a lot less noticeable. Rotobrushing is going to take way too long to process...he wants me to spend only about an hour on each one, and it's taking near an hour to even propogate an area (because the range is 2 minutes....

Now, the option 3, Difference Matte, to use that, I would need an instance of the greenscreen without the person, right? And I'm currently doing something like method #5 now, along with selective color to boost the green.

*sigh* When I took this job, I was hoping it was good GS footage.


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Joseph W. Bourke
Re: Is there any hope for this greenscreen? Any methods I can do to fix the "static fringe"?
on Aug 7, 2013 at 11:31:03 pm

Jeff -

I know it's too late to do this, but you should have had a look at the footage to make sure that it was doable in the allotted time. If your client is reasonable, you might be able to go back to him and tell him that there are technical problems with the footage, and it's going to take longer (cost more). I know how that goes, and I've been in the position before - sometimes if you approach someone hat in hand, and are honest with them, they'll allot some more time/expense. Sometimes not...

I haven't had much luck with the Difference Matte, but yes, you need what they call a "clean plate", the shot, with identical lighting, and no actor in it. Here's a rundown from the Adobe help:
http://help.adobe.com/en_US/aftereffects/cs/using/WS3878526689cb91655866c11...

Joe Bourke
Owner/Creative Director
Bourke Media
http://www.bourkemedia.com


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