What would you make of this output from drawChessboardCorners?

3

I think the algorithm is just meant for images where the calibration board is no less that 1/4th the viewport/image, that’s all. Is also seems that also all web examples I happened to gloss over out there for calibration with checkerboards, present the board relatively up-close to the camera. Clearly the hard-coded circles radius is no fit for when the board takes only around 1/16 of the image. Mathematically it doesn’t have to be so, but I guess the standard implementations assume it. Still learning.