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Chroma keying & Motion Blur

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Andre van Berlo
Chroma keying & Motion Blur
on Dec 24, 2013 at 11:47:05 am

Hey everyone,

I've been using FCPX since it came out and lately I've been doing chroma keying with it. It works nicely and I'm getting better at setting everything up correctly to get the better/best results out of my cameras (1 GH2, 2 GH3's, and a panasonic handycam).

I've noticed in quick movements of my hands and arms that there is a green haze on the edges of my skin (where the image of my hands 'touch' the image of the green screen - in my case a wall painted green). My guess is this is due to motion blur, but could it be something else?

The GH2 & GH3 record in 4:2:0 so that might be a culprit. But would it help to shoot at higher frame rates and/or faster shutter speeds?

Any suggestions are welcome!

André


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Michael Sanders
Re: Chroma keying & Motion Blur
on Dec 26, 2013 at 10:15:29 am

I had this on a recent edit - I've never seen it before but I guess a higher shutter speed would sort it.

Our material was 1920 x 1080 25p and they should have had a 1/50 shutter in.

Michael Sanders
London Based DP/Editor


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Andre van Berlo
Re: Chroma keying & Motion Blur
on Dec 26, 2013 at 10:40:29 am

Thanks Michael, I'll try that!

Reason why I'm seeing it also has to do with the fact that my iMac is way to slow so sometimes I'm experiencing extreme lag. Then that green haze gets very noticeable. Less when the video is playing real time. I've got the shutter set @ 25fps now but I'll try 1/50 to see that it does, also maybe 1/100. It'll mean shallower depth of field so hopefully it doesn't get too bad

Thanks again!


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John Fishback
Re: Chroma keying & Motion Blur
on Dec 27, 2013 at 6:10:52 pm

Have you tried adjusting the Spill Level? That might help. It adds magenta to cancel out the green.

John

MacPro 8-core 2.8GHz, 16 GB RAM, OS 10.8.4, QT10.1, Kona 3, Dual Cinema 23, ATI Radeon HD 5870, 24" TV-Logic Monitor, ATTO ExpressSAS R380 RAID Adapter, PDE enclosure with 8-drive 6TB RAID 5
FCS 3 (FCP 7.0.3, Motion 4.0.3, Comp 3.5.3, DVDSP 4.2.2, Color 1.5.3)
FCP-X 10.0.9, Motion 5.0.7, Compressor 4.0.7

Pro Tools HD 10 w SYNC IO & 192 Digital I/O, Yamaha DM1000, Millennia Media HV-3C, Neumann U87, Schoeps Mk41 mics, Genelec DSP Monitors, Prima CDQ120 ISDN


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Andre van Berlo
Re: Chroma keying & Motion Blur
on Dec 27, 2013 at 9:41:18 pm

Hey John , thanks for your reply,

Usually I drag the Spill level slider all the way to the left (that's 0 right?) exactly because of that weird tint. Probably because I use GH3 cams that only have 4:2:0 colour space. In fact, I realised that my old panasonic hdc-sd60 is actually easier to use for chroma keying than my gh3, I have no idea why though…

But I'm curious, when you use spill level, do you colour correct the magenta?

André


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