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Which camera would be best for motion tracking?

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Jeremy Chopra
Which camera would be best for motion tracking?
on Sep 5, 2012 at 5:05:49 pm

Hi all,

Not sure which forum to put this question on as its quite a broad general question I guess..

I need to rent a camera and want to get the best one for motion tracking that will have minimal motion blur so the track is solid, a camera that isn't too expensive and importantly not too BIG as it will be filmed handheld and the smaller the more steady we will be able to get it.

Any suggestions?

Would a DSLR like the Canon 5 or 7D be good enough? Any known issues with motion tracking off footage shot on one of these? or something like the XF305?


thanks

http://www.cascadepictures.co.uk


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Todd Terry
Re: Which camera would be best for motion tracking?
on Sep 5, 2012 at 6:31:43 pm

I don't really know any particular camera that is better specifically for motion tracking than another... as far as that goes most cameras are pretty much the same. Motion tracking and its quality is much more a function of the tracking software used... the the operator doing it.

If you are trying this and motion blur is causing tracking problems, then that issue is easily corrected by just shooting at a higher shutter speed. BUT... of course you run the risk of choppy/juddery-looking footage (the "Saving Private Ryan" or "Gladiator" effect), because the brain needs that motion blur to interpret footage as smooth.

I would suggest shooting progressive rather than interlaced, but of course that is more dictated by the "look" you are wanting for the project.

A 5D or 7D can certainly shoot 24p, and of course you can adjust your shutter speed on those cameras very easily. Again, though, remember that "normal" shutter speed (emulating a 180° shutter on a film camera) is "one over twice the frame rate"... therefore at 24p the "normal" shutter speed would be 1/48th. You can crank that up to eliminate the motion blur if that helps you track better... but again, the footage might look a bit too crisp and choppy.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Jeremy Chopra
Re: Which camera would be best for motion tracking?
on Sep 5, 2012 at 9:18:09 pm

Hi thanks for the response..

I am fairly good with motion tracking but have had issues with some cameras that due in part to their compression and a lot to do with their motion blur kind of bend the image in places (tech issue or design issue I don't know) but that bending makes it impossible to track without a LOT of manual changes so the workflow and is effectively far too damaged to warrant even working on in any realistic time scale.

I don't want to effect the image in any way as would do that in post also. so shutter speed I guess might be out of the options here. I just need as crisp and clean an image devoid of motion blur so the tracker can find the pixels and not lose them in movement. Even with Boujou badly blurred and randomly bent pixels cause a lot of issues so am trying to minimize that really.

I guess if there is no real clear winner in regard to the best camera then a list of those to steer clear of might be a better way to start to figure out what to go for so any suggestions on that are also much appreciated..

Jeremy

http://www.cascadepictures.co.uk


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Todd Terry
Re: Which camera would be best for motion tracking?
on Sep 5, 2012 at 9:49:09 pm

Ah that "bending" you a speaking of is probably due to a "rolling shutter effect"... which is especially seen on vertical lines during things like fast pans. I've never heard of anyone having tracking issues with a rolling shutter, but I think it's certainly possible. The problem with that and tracking is if you do get that bending, you'd want your tracked element to bend along with it to look real... otherwise it would give away the composite.

There are two kinds of camera shutters... "rolling" and "global." A rolling shutter basically "draws" the picture on from top to bottom of the frame, much like scan lines in an interlaced TV. The problem with that is, during fast moving shots (especially pans) the scene is in slightly different positions at the bottom and the top. It captures the frame at the top, but by the time the shutter reaches the bottom the shot is in a different position. When panning most noticeably vertical lines slant, because the tops and bottoms are in different positions. A GLOBAL shutter, unlike a rolling shutter, basically "snaps" all the frame at one time, eliminating those slanty and bendy lines.

You'll mostly find rolling shutters in CMOS sensor cameras such as DSLRs. Global shutters are more common in CCD cameras, such as "real" video cameras (not DSLRs). It may be that you can solve your issue by shooting with a camera with a global shutter, and discounting any with rolling shutters. There are exceptions, but to put it broadly that would mean not shooting with a DSLR and instead shooting with most any "regular" video camera.


[Jeremy Chopra] " I just need as crisp and clean an image devoid of motion blur"

Well as I said in my previous post, that's pretty easy... just crank up the shutter speed until you get crisp frames with no motion blur. 1/250th or higher should do it. Again though, keep in mind that you'll get juddery/stroby-looking video if there is fast motion in your scenes. Our brains and eyes need that motion blur to interpret it as smooth motion. Otherwise the too-crisp frames look very choppy when played in full motion.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Jeremy Chopra
Re: Which camera would be best for motion tracking?
on Sep 17, 2012 at 10:57:04 am

Thanks Todd

Sorry for the delayed response, have had a lot of work come in out of the blue so just getting back to this project now.

Everything you described is spot on with my issues. I did wonder if it was down to an interlacing problem and makes sense that that is the reason now.
Creating that bending on the composite layer is very difficult and time consuming so will go with a non-DSLR camera just to be safe then.
Are there any DSLRs that are progressive scan out now or on the horizon?

I intend to degrade the footage in post for a "consumer" camera 'look' anyway so just getting a good track and a depth in the footage is what I really need so the next step is finding the best CCD camera that will do the job at the lowest rental price possible.

Thanks again

Jeremy

http://www.cascadepictures.co.uk


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Sareesh Sudhakaran
Re: Which camera would be best for motion tracking?
on Sep 6, 2012 at 3:56:21 am

Jeremy, you'll want the camera with the best resolution for motion tracking.

If you are good at it, then you will be frustrated by the line skipping resolution from DSLR cameras - stay away from it - unless you are using something like Nuke or Boujou, etc that can handle poor video.

Take a look at the Sony FS100 - and shoot at 50/60fps to eliminate 24p motion blur - the footage can then be retimed to 24p or whatever the delivery frame rate is.

At this budget the temporal resolution from the FS100 and its pixel pitch resolution should offer the best bet. Hope this helps.

http://wolfcrow.com/blog/ - Workflow information and support for filmmakers, photographers, audiographers and videographers.


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Jeremy Chopra
Re: Which camera would be best for motion tracking?
on Sep 17, 2012 at 11:02:32 am

Thanks Sareesh

Seems the consensus is to go with a CCD camera and not DSLR so will likely try your suggestion. I will also definitely be shooting at the higher frame rate and changing in post.

Thanks again really appreciate the suggestions and advice.

Jeremy.

PS When the project gets completed I will post the results..

http://www.cascadepictures.co.uk


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Paolo Castellano
Re: Which camera would be best for motion tracking?
on Sep 18, 2012 at 10:08:14 pm

Hi Jeremy,
there are some CMOS cameras that are "rolling shutter" free, like Canon XF300/305 and C300 (and probably the new ones from JVC). I'd choose one of these new designs instead of an old (but still good) CCD camera. The 4:2:2 50Mps recording data-rate will help to reduce the artifacts.

Best Regards,

Paolo.Castellano@ivs.it
http://www.ivsEdits.com
-----------------------
"Post Fata Resurgo"


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Jeremy Chopra
Re: Which camera would be best for motion tracking?
on Sep 22, 2012 at 11:05:08 am

Thanks Paolo

I have been wanting to try the XF305 for a while on a project and it looks like that may be the winner for this one. I just wanted to cover the possibility of problems in post and get a nice look too of course so all in all everyone has been a massive help on this decision.

Thanks all

Jeremy

http://www.cascadepictures.co.uk


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