[Bf-vfx] Footage for Tracking

Wed Jun 8 20:53:12 CEST 2011

Yeah, rolling shutter is an *incredible* pain.  It can be corrected to an extent with tools like The Foundry's "RollingShutter" plugin for Nuke, which I've heard can make previously un-trackable shots trackable, but you see it *everywhere* these days -- even in hollywood features.

I do have some footage I can get you from my Canon XH-A1, which is a 3-CCD HDV camera.  I sold the camera recently (CMOS is all the rage!), but I have a ton of footage I can go through.

That said, RED's CMOS sensor is waayy better than the "jellocam" sensors in DSLRs like the 5D or T2i.  (RED's new MX sensor I think is even better).  So the rolling shutter is not bad -- but it's still noticeable in very high-motion shots.  

I'd say 80% of the RED shots I've got should not pose issues due to rolling shutter.  The tracking tools I've been using do not account for rolling shutter, yet I'm able to get very solid tracks with little manual intervention.  So perhaps still valuable to test with?

--Colin

On Jun 8, 2011, at 2:32 PM, Keir Mierle wrote:

> Thanks Colin!
> 
> One point though: RED uses a CMOS sensor and is subject to rolling shutter. Do you know how bad it is? Some cameras have very slow sensor readout (and so terrible distortions with movement) and others have a faster rolling shutter which still has distortions, but less.
> 
> For those who don't know: rolling shutter means that each scanline has a *different* shutter time! Yes, that means that the image is composed of 1000's of images, one scanline taken from each, with the camera moved between images. Extremely annoying, and totally breaks all the camera tracking assumptions.
> 
> I realize that we have to handle rolling shutter but it's a big job and we won't support it in the first release.
> 
> So I repeat my request: does anyone have a camera that doesn't have a rolling shutter? For example, the Panasonic SD9 has a CCD sensor and so takes true pinhole images for each frame.
> 
> Virtually all modern DSLR's have awful rolling shutter (D90 included), so they are also excluded.
> 
> Keir
> 
> On Wed, Jun 8, 2011 at 11:00 AM, Colin Levy <colin at peerlessproductions.com> wrote:
> Hey guys,
> 
> I've got several TB worth of 4K material I can offer for tracking.  However, the shots will represent a more "real-world" scenario rather than the test case shots listed below.
> 
> I don't suppose you want the RED .r3d files, so will TIFF sequences work for you?  (Or do you want both?)  I will go through my drives in the next few days and upload a few shots to my FTP, if you think this would be useful!  Let me know whether you'd like 32-bit images, with all the 'RAW' data intact, or if 8 or 16bit will suffice.
> 
> One thing to note regarding resolution: I have noticed that in many cases, tracking downrezzed shots is frequently more successful than trying to track the raw 4K material.  This may have something to do with the default values (the default auto feature search range, for example, may be something like 20px rather than 80px, which might be a better setting for 4K).  For my projects I usually downrez to 2K before tracking... also because it's a lot faster.  :P
> 
> Great discussion.  Can't wait to see these tools develop!
> 
> --Colin
> 
> 
> On Jun 8, 2011, at 12:59 PM, François T. wrote:
> 
>> I'll do all that on saturday with D90. 
>> 
>> cheers
>> F. 
>> 
>> 2011/6/8 Keir Mierle <mierle at gmail.com>
>> A catalog of the following shots would be useful:
>> General motion: Moving and rotating camera. Camera is /not/ always pointing at one part of the scene.
>> Rotation only: camera on a tripod, rotating around a fixed point (if possible the camera's "Nodal point", but you need a special tripod for that)
>> Translation only: walking sideways keeping the camera pointed forward (e.g. not circling)
>> Translation only: walking towards the scene
>> General motion when the scene is planar (e.g. camera keeps a big billboard in view and only the billboard)
>> Circle strafing around an object; camera is fixated on one part of the scene (intersecting principal ray)
>> The scenes should have good texture so that tracking is easy; we can add challenging scenes later. It's ok if the translation-only scenes have some hand held wobble; that's fine. Boxes with texture are good. Complicated objects like bushes or trees are bad. The scene must be static (no cars, people, birds, godzilla, etc).
>> 
>> The camera must be calibrated. There is a libmv calibration target that you can affix to a really flat object. The calibration target must be really flat; something that has a bit of bend is unacceptable and will give poor results.
>> 
>> http://libmv.googlecode.com/svn/trunk/extras/calibration/calibration.pdf
>> 
>> Take several images of the calibration target (or a video in HD). Get different rotations and fill the frame to get the edges (important for distortion correction). Then run one of the calibration tools to find the intrinsic parameters (focal length in pixels, distortion, skew, etc).
>> 
>> Note: Rolling shutter is *horrible* for tracking. We're going to have to handle it at some point, but I am trying to avoid it as long as possible. Do you have access to a CCD style camera without a rolling shutter?
>> 
>> Keir
>> 
>> On Tue, Jun 7, 2011 at 3:27 PM, Ian Hubert <ian at projectlondonmovie.com> wrote:
>> Hey all! 
>> 
>> I've been following the conversations, and wanted to throw out that if anyone needs any sort of footage, I can run out and film stuff. I already have a few things things filmed- mostly just walking around the city holding the camera as steady as I can- but if anyone wants anything else (underexposed, really shaky, steady smooth, panning--but-no-movement, somebody walking across the frame, stuff like that), just say so!
>> 
>> At this point all I can quickly provide is SD and HD- I unfortunately don't have access to a 4k camera, but I'll film some random stuff if I ever get my hands on one. 
>> 
>> -- 
>> Ian Hubert
>> 
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>> -- 
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