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 Post subject: 8 cam calibration
PostPosted: Fri May 30, 2014 4:42 am 

Joined: Mon May 26, 2014 2:10 am
Posts: 24
Hi my friends.
At the moment I'm trying to get a working 8 cam setup. I have 8m to 6m space.
I tried to put the cameras in a square to get as much as i can in the field of view of all cams. I have different heights (starting 30 cm looking up till 3,3m ). The problem is, even though I have this much space it's not possible to get a proper area where the light is always in every camera. So my thought is, could I calibrate just the 4 corner cameras and then align the other 4 to them in some way? Do I really have to be always in every camera when using 8 cams?
Or if that's not possible could it help to put the other 4 also near the corner in different heights and angles, to get more space, or is a full circle better although I don't get the full space?

Thank you very much :)


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 Post subject: Re: 8 cam calibration
PostPosted: Fri May 30, 2014 5:46 am 
iPi Soft

Joined: Wed Jan 11, 2012 6:12 am
Posts: 2355
Location: Moscow, Russia
Naturally, when doing calibration, sometimes the light marker is obscured from some of the cameras by a person holding it. For successful calibration, you need to maximize the number of cameras that the marker is visible to, at any given time. Here are some tips for this:
  • Hold the marker away from the body (in a straght arm)
  • When following the upper part of capture volume, you can hold the marker above your head to ensure full 360 degrees visibility, squating if needed.
  • When in the lower part of capture volume, especially marking groundpoints, hold the marker closer to the center of a capture area, and your body away.

When recording an action video, it's better to have an actor visible to all cameras at all times. However, if he's only partially visible in some cams, that may be tracked OK.
In that sense, full circle setup looks preferable over "2 cams with different view directions in each corner".


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 Post subject: Re: 8 cam calibration
PostPosted: Fri May 30, 2014 6:28 am 

Joined: Mon May 26, 2014 2:10 am
Posts: 24
Thank you :) So if I got it right, I try to calibrate just the area where the flashlight is save in every camera and when it comes to capturing I try if i still get it tracked right if i leave the save 8 cam area where just 6 cams or so are save?

Thank you :)


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 Post subject: Re: 8 cam calibration
PostPosted: Fri May 30, 2014 12:55 pm 

Joined: Mon Aug 03, 2009 1:34 pm
Posts: 2423
Location: Los Angeles
I haven't used an 8 camera setup but you might try attaching the Maglite to a long boom to minimize occlusion. I read elsewhere in these forums that some users have had good results from it.

G.

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 Post subject: Re: 8 cam calibration
PostPosted: Sun Jun 01, 2014 3:05 am 
iPi Soft

Joined: Wed Jan 11, 2012 6:12 am
Posts: 2355
Location: Moscow, Russia
Yes, you should not put the light marker outside a "visible to all cameras" area.
Yes, you can leave a "visible to all cameras" area, but the number of tracking errors may increase in such cases.
Take Greenlaw's advice about mounting the light marker on a stick if you experience troubles with occlusion of the marker during calibration.


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