[ros-users] camera_calibration

[Eric Perko]

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 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?

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.

- Eric

On Tue, Apr 6, 2010 at 4:46 PM, Patrick Beeson <beeson.p at gmail.com> wrote:
> I checked out latest and had to do a small bit of changes to sync the
> timestamps of the two cameras whenever frames have very close
> timestamps.  So they aren't EXACTLY synced, but VERY closely synced.  I
> can try to send you a screen shot of the output.  Note, I am testing
> this with a quite small checkerboard (your checkerboard, but with 26mm
> squares).  Maybe that's the problem?  Maybe I'm sampling a space too
> close to the cameras?
>
> Eric Perko wrote:
>> Patrick,
>>
>> What version of camera_calibration are you using? Boxturtle?
>>
>> - Eric
>>
>> On Tue, Apr 6, 2010 at 4:31 PM, Patrick Beeson <beeson.p at gmail.com> wrote:
>>> I'm trying to calibrate two identical 1394 cameras that are sitting next
>>> to each other.  The stereo calibration from camera_calibration converges
>>> to VERY bad R and T matrices, rotating the frames and
>>> the warping the images drastically.  I've tried several times, with no luck.
>>>
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