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Green Screen Techniques
This is a question about camera movement during a green screen shoot. I’ve got a music video shoot coming up and a lot of it will be shot in front of a green screen. If you make any camera moves while shooting, when the background is keyed, it’s relative size remains constant behind the subject – the perspective doesn’t change during a zoom or pan. I understand this, and realize that it makes for a jarring effect. How do they do camera movement in high end productions? It can’t all be manipulated in post. For example, the camera does a 180 degree tracking shot around the subject and the keyed background changes perspective accordingly. Unless the keyed background is a solid color or pattern, how is perspective altered?
No hurry – just something I’ve been thinking about.
G5 – 2GIG DUAL – 2GIG RAM
FCP; AE; PS; DSP -
7 Replies
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Well you picked a tough thing to do… in high end productions they use tracking markers and special software to compiste the tracks to derive the camera movement. In order to do this you really should use a motion control rig such that you can replicate the move over and over for various elements. Also it allows you to build a replica in the computer and get exact matches without green screen tracking markers… but if you can’t do that then its off to buy some tracking markers, and either find some software, or have fun doing the math…
Simon Carlson-Thies,
Digital Light Graphics And Animation -
I love it! Great.
I’d be interested in all other comments as well, while I am brushing up on my math skills!-Mike
G5 – 2GIG DUAL – 2GIG RAM
FCP; AE; PS; DSP -
Here’s an article from DV magazine on matchmoving: https://dv.com/news/news_item.jhtml?LookupId=/xml/feature/2006/christiansen0306
You should be aware that even with the best software, it’s a time consuming process that requires a lot of hand work. Also, a lot of this is done with backgrounds that originate in 3D software.
Arnie
https://www.arniepix.com -
Many people put talent/performers on a turntable… spin talent… viola!
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This could be done with After Effects or Commotion.
You’d need to put markers on the green screen background which are then tracked by software in post.
This would give your compositing software an idea of where the background was in relation to the foreground object.
After you’ve keyed your model you then use the motion tracking data to lock your background to the original green screen. Of course you’ll have to also remove the tracking markers that weren’t keyed by the keying software but that can mostly be handled with a garbage matte.
Keep in mind that the markers will give you relative motion assuming the background elements are also where the green screen actually was. So if your background plate was supposed to be a lot farther back, you’ll have to modify your tracking data to ensure that the relative motion of your background is correct.
I also saw this being done in real time at the Ultimatte booth at NAB. The background was generated in 3D in real time and composited with the foreground model. The camera was being moved at random and its movements were also being tracked and applied to all the elements in the composite. Was very impressive.
Dean Sensui — http://www.HawaiiGoesFishing.com
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[Dean Sensui] “This could be done with After Effects or Commotion.”
Depending on the kind of camera movement you need matchmoved. For anything much more complicated than a track or pan, you need 3D matchmoving software such as Boujou, Matchmover, or the tools found in Inferno and Flame. We use PFTrack, which works well, and I’ve heard good things about SynthEyes at the lower end of the market. You’ll need a 3D app or compositor (ie. Nuke) to integrate all of the various elements.
Practical tip: use blue tracking markers: you can then get rid of these with a second key. Beats roto …
Good luck!
Tom
Split Image
http://www.split-image.co.uk -
You should check-out the video here: https://www.ryantown.com/gayboyfriend/
It’s been around awhile, but it still looks great, and the director has a good “how-to” that provides excellent tips on green screen techniques.
Motion control may be a bit much to bite off for your first green screen experience.G5, Dual 2GHz, 1.5 GB Ram, OSX 10.4.6, FCP5.1, AJA Io, SATA External Array 500 Gig
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