Is there a database of common camera parameters anywhere?
I've been successfully using OpenCV for an AR application for several months.
In debugging some minor registration errors that I see on certain platforms, I'm sometimes unsure that the camera parameters for that device are correct, in that I may have given poor input images when measuring calibration. My camera parameters are generated using the standard openCV camera calibration (calibration.cpp).
When I say that these calibration errors are minor, I mean that drawing a planar quad in 3D space using the 3D coordinates I extracted from 2D features in the image matches very well. But extending that coordinate system beyond the bounds of the square marker starts to diverge (straight lines in image space are not quite straight lines in world space), implying that the coefficients used to remove radial distortion from the image aren't quite correct.
I'm particularly interested in consumer cameras - Logitech externalwebcams including the C910, iOS, and recent Android cameras.
So, I guess my questions are:
1. Is there a database of camera parameters publicly available anywhere? It would seem that the number of people who have independently measured, say, the iPhone 4 camera's parameters is in the thousands...
2. Is there any way to look at the output of a given calibration run and determine a confidence level that the parameters generated are correct?
3. I've heard that there are other calibration patterns rather than the standard chessboard with calibration.cpp that produce more reliable results. Is this true and should I be looking at them?
Re: Is there a database of common camera parameters anywhere?
I ran into some of the same issues. I'm not aware of a camera calibration database, but this seems like an obvious need. If you find one, please post back. Perhaps an ad-hoc one could be started by simply posting matrices for various models on the OpenCV forum.
The lack of repeatability and documentation of the OpenCV camera calibration program can be a bit frustrating. I searched around and found something better:
It guides you visually on how to hold the calibration pattern, then produces better and more repeatable results. It's written in Java and works with local cameras as is. I got it to work with IP cameras by modifying the ffplay utility to send video to AprilCal.