[ros-users] camera_calibration

Patrick Beeson beeson.p at gmail.com
Tue Apr 6 21:21:57 UTC 2010

Sony xcd-sx90c cameras with Fujinon lens.

I've done this same process with the MATLab camera toolbox and it worked 
great (other than having to manually click all the corners).  This is my 
first attempt at using the opencv functions to calculate parameters.

Eric Perko wrote:
> Hmm... dunno... I'll try it out on my cameras tonight and get back you
> with the results. What type of 1394 cameras are you using?
> On Tue, Apr 6, 2010 at 5:15 PM, Patrick Beeson <beeson.p at gmail.com> wrote:
>> Eric Perko wrote:
>>> Have you tried different baselines to see if that affects the
>>> calibration results at all? And I'm pretty sure my checkerboard has
>>> 28.58 mm squares, so yours is not that much smaller. Can you try a
>>> larger checkerboard?
>> I'd have to print one.  I've tried this multiple times and at a variety
>> of distances.
>>> I'd assume that, if your cameras are not moving and you can hold the
>>> checkerboard still until both cameras have taken a pair, syncing
>>> shouldn't be a huge problem for calibration. What happens if you
>>> calibrate each camera separately and view rectified images? Do they
>>> come out okay or are there issues with monocular calibration as well?
>>> Specifically, does that checkerboard work for monocular calibration?
>> Yes.  Monocular works fine.
>>> Also, some other students working on stereovision using OpenCV
>>> directly have found that you have to be careful while watching the
>>> calibration to make sure that the corner detection is working
>>> properly. For example, if it begins by marking corners in red on top
>>> in both cameras, it has to always mark the top corners in red - if
>>> they ever flip or otherwise change orientation, it will make things go
>>> quite funky. I've seen it happen with my monocular calibrations if the
>>> person with the checkerboard isn't careful and accidentally lets the
>>> checkerboard rotate along the axis from the camera to the
>>> checkerboard.
>> Didn't happen.
>> Problem is that R and T are retuning VERY high values.  I just went from
>> trunk to latest, added a small fix to the node source to only accept two
>> images if there timestamps are within 0.05 seconds of each other, and
>> tried again.  With latest, I get even larger crazy values in R.  Again,
>> I can send the output tar file, which I assume you can run through in an
>> offline manner, and you can see that the checkerboard is proerly found
>> on all used frames.
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