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Green Screen Key
Hello all,
I have just been given some footage from several different camera angles. Some are QT some are QT rerendered as AVIs, the file properties for both are as such:
QTs
Image size 1280 x 720
Pixel Depth: 24
Fr Rate 29.97
Av Data rate: 3.6 mb / sec
Pixel Aspect Ratio: 1.212
created with AEAVIs
Image size 720 x 480
Pixel Depth: 32
Fr Rate 29.97
Av Data rate: 29.6 mb / sec
Pixel Aspect Ratio: 1.2
created with AEThe issue is, The key lighting isn’t that great. Their are alot of shadows that are hard to get rid of. When I key the resized AVIs I get stepping along the edges of the keyed images. Also, their are white tape markers on the walls and floors of the green room that obviously stay in the picture when keyed. I know these are their for a reason, I assume for some kind of 3d motion tracking? I am using AE to do the keying using the Key light filter. How can I get rid of some of the shadows without dropping too much picture information that I want to keep? How do I get rid of the stepping? And how do I properly use the tape markers for pinning floors and walls or get rid of the tape marks all together?
Any professional suggestions would be greatly appreciated. I am sure some of you are rolling your eyes at these questions. This is my first experience with this kind of situation and my boss threw me to the wolves on it (hes not a video professional). Any real help would be great. If your wanting to use this posting as a platform for you to voice a disgruntled attitude or to be self exhalting without actually subbmitting any usefull information, please don’t bother.
Thanks everyone. Best success to you all.
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9 Replies
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Heh. 🙂
It sounds as if your AVIs are DV, no? If so, you may wish to try DVMatte Pro, as I’ve heard it does a good job of keying DV.
Regarding the tape markers, those are best used as guides for 3D Matchmoving software such as Syntheyes. It tracks the markers in 2D, then does nifty calculations to create a 3D scene and camera for export to a 3D app or AE. Great stuff.
But to use AE to make sense of those, you need to track four markers that make a plane, then basically glue those tracked markers to the corners of a layer in AE. It works well for TV screens, windows, billboards and painting frames, but I’m not sure what they want you yo do with them. I recommend Syntheyes, anyway.Anybody else?
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Steve,
Thanks for such an immediate response. Very appreciated. Yes this was all shot DV. Have you used the DV Matte pro plugin for AE?
As far as the 3d goes, I am stuck using AE for this. Their is zero budget. What I have been requested to do is to take alternate video files of the same properties and use them as the floor, walls and ceiling for the key video. How does one “glue” something to these markers? Is their a tutorial on this I can view?Thanks a ton Steve, this was extremely helpfull.
Once again, Best success to you.
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If I recall, I tried the DVMatte demo and was pleased… but sorry, I actually rarely key. There may be some more tips on the COW — if you search the articles or posts for “DV” and “greenscreen”, you should find something.
As for the markers … you open the tracker controls, choose perspective corner pinning, choose your replacement footage as the target, drag the tracker points over the four markers, move the current-time indicator to the point where you want to start tracking, then press the play button next to “analyze”. Then you stop it when you want. Then you press “apply” to apply the tracking to the replacement footage.
I’d imagine the problem would be: finding four trackers that make a plane. If they do make a plane, but the plane is too small or big, you can always apply effect>distort>transform to the footage, keeping it below Corner Pin in the effects stack. The scale up/down your footage in the Transform effect controls.
Now if the camera is static, you could fake it by applying the distort>corner pin effect to the replacement footage, and distort it until it looks right to your eye.
Does that make sense?
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… and there should be a Motion Tracking tut on the AE COW … ?
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Steve,
Thanks for all the advice, it is very helpfull. I have found a trial version of DV Matte pro and will give it a shot. I have done some motion tracking before but not to this extent. Your instructions
of how to execute this are extremly helpfull. Thank you. I am going to dive into this now. I will let you know how it turns out if your interested.Once again, my greatest thanks!
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Hey, no problem. Let us know how it goes.
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Steve,
I ran into an issue. Their seems to be no DV matte pro for PC.
I am on a Dell precision 690. Any suggestions? -
Wuzelwazel posted the chrominance blurring technique recently:
“You can blur the chroma in After Effects by applying Channels > Channel Combiner and setting it to RGB to YUV, then apply Blur > Channel Blur and set the Green and Blue blur values to something like 0.5 (more or less as needed), then apply another instance of Channels > Channel Combiner and set it to YUV to RGB. This will blur the chroma (UV) of the footage and should make for less blocky edges when keying.”
Hope it helps. Otherwise, you could search the COW AE forum (advanced, archives) for “DV” and “greenscreen”.
Hope it helps …
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Steve,
Thanks for all your help on this. In the end I didn’t use the motion tracking to pin video to the walls and floor. It just wasn’t the right option for this piece. I went with a straight key with a white background. I wanted to treat the video so it looked like film and bring the colors out. It seemed right for the video. So I put some suttle compositing effects in to compliment the color intensities and to give the piece more life. I used keylight, matte choking and blurring to get rid of the stepping. I think it all turned out very clean and sharp. I was very pleased with the end result and tried to let the edit drive the piece and have the efx compliment the edit. You can view it at
https://www.brightcove.com/title.jsp?title=979724176
Let me know what you think.
Thanks again for your help, Best success to you!
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