It has been surprisingly difficult to find good opencv calibration patterns. I had found what I though was a good calibration image and ended up wasting my time. Turns out that file does not consist of squares. So I ended up making some high resolution PNG files for camera calibration. The sizes of the patterns refer to the number of features (corners) and not the number of squares. So the 8x6 pattern consists of 9x7 squares.
- 8x6 pattern with 20mm square size
- 9x6 pattern with 20mm square size
- 15x11 pattern with 30mm square size
Not a big deal, but it is nice to be able to grab one of those whenever you need them.