Camschnappr new parameters?

Anyone found a good description of when you would use the extra Camschnappr parameters, such as:

Intrinsic guess, fix aspect ratio, zero tangent distance, Fix K1, K2, K3?

All I can find is: docs.opencv.org/2.4/modules/cali … ratecamera
Which presumes you know what they all are, as far as I can tell.

I know principal point boils down to what I would call ‘lens shift’, so I’m guess that fixing that point is specifying that I have a ‘perfect’ lens that projects an image directly centered… and I think the K1,2,3 are something to do with very short throw lenses or maybe radial distortion (which camschnappr doesn’t handle anyway).

Bruce