Shooting for Green Screen and Motion Tracking
by Neal Sickles (Icicles)
on
May 5, 2008 at 7:56:45 pm
Can anyone refer me to a tutorial on shooting motion (pan/tilts/zooms/dolly) green screen and the workflow in post or provide any advice, please?
I'm working on a video for a client and have amazing ideas but am limited by my experience in shooting camera motion on green screen. What can I do to prepare for my shoot and what are my options for motion tracking in post?
I hate to give the stock answer, but a quick google search of green screen shooting tips, or shooting green screen for motion tracking should get you going..
Re: Shooting for Green Screen and Motion Tracking by Neal Sickles on May 6, 2008 at 12:16:24 am
Thanks Jeremy, I have seen that article and it helped a little, but I'm going to be trying to match my live action and camera movement with the background virtual environment and this article doesn't explore that.
I've searched around the web and looks like I can pull it off if I set the camera on a tripod and don't make any movements (safest bet). I could then place a background image for my environment and adjust it as needed.
However, since I would love to move the camera, if anyone can offer any advice or a workflow for this I would really appreciate it and I'm sure you'd be helping many others on this.
I'm equipped with FCP Studio 2 and AE CS3. Not completely sure if I have the tools for motion matching or if I need to invest in a 3D camera tracking software like Boujou Bullet or SynthEyes or even a 3D character application like Maya.
Re: Shooting for Green Screen and Motion Tracking by Darby Edelen on May 6, 2008 at 12:55:37 am
[Neal Sickles]"What can I do to prepare for my shoot and what are my options for motion tracking in post? "
This depends largely on what you're trying to accomplish. AE's motion trackers are 2D trackers exclusively, so you are very limited as to what you can accomplish in AE alone.
If you don't have experience tracking things in to greenscreen footage (or vice versa) then I would highly recommend starting simple and doing some tests. You will want to have some tape on the screen to use as tracking points regardless of the scope of your tracking endeavor, but keeping it simple early on will help you learn what works and what doesn't before you're spending your clients time & money on something.
I don't recommend getting too deep into heavy tracking, but you should definitely do some research in that direction online. Download some demos and get some books on the subject. Here's some info to get you started:
There are applications out there that will allow you to create 2D trackers to determine the properties/motion of the camera that was used to film the scene. This is generally referred to as a matchmove and there are many applications that can be used to matchmove your footage. I like SynthEyes because it's fairly accessible and relatively inexpensive:
Programs such as SynthEyes will export camera data in a wide variety of common formats, including Maya (.ma) files that AE can import and apply to an AE camera. In order to get the best matchmove possible you'll want to record data about the camera you use (lens focal length, height from the ground, distance from subject, etc) to help both you and whatever application you happen to be using.
I recommend checking out Matchmoving: The Invisible Art of Camera Tracking if you're interested in doing more research/reading on the subject:
Re: Shooting for Green Screen and Motion Tracking by Joey Foreman on May 7, 2008 at 2:02:55 am
The HVX-200 shoots in DVCPro format which utilizes 4:2:2 chroma subsampling, as opposed to HDV's 4:2:0. I've never seen a side by side test of keying DV vs. HDV, but i'm almost be willing to put my money on the DV, given that HDV is more compressed.
And DV is already poor source material for keying footage.
Some will say that Keylight in AE will pull a good key from DV, but I doubt that key would hold up in a myriad of compositing scenarios. Might look okay against certain tones, but it's still going to be over-jagged, noisy, or over soft around the edges.
And honestly, not even 4:2:2 will give you perfect keys for every scenario.
So try to go with the best you have access to.
Joey Foreman
Editor/Animator
Nowhere Productions, Athens, GA
Re: Shooting for Green Screen and Motion Tracking by Joe Moya on May 6, 2008 at 12:40:57 pm
There are a lot of tutorials on both of these subjects - green screen and tracking...
These are two highly effective way of creating unusual effects... IF they are done correctly... If done incorrectly it can look cheesy.
A few hints...
Green screen... Lighting is crucial. Shadows are problematic.
Tracking... Patients is crucial. ...Time consuming.
For tracking and rotoscoping, I use Mocha by Imagineer... it is light years ahead of many other tracking or rotoscoping software... but, it is very expensive.
Re: Shooting for Green Screen and Motion Tracking by Neal Sickles on May 7, 2008 at 7:17:21 am
Thanks everyone. I've learned a lot from your input. I will be testing in a week or whenever funds come through. I'll let you know if I come across any significant discoveries.
