Thanks. I’m also aware of the description from the book. However, it is rather incomplete and also does not provide any references for the lens model. I’m also wondering what are “exotic lenses” and why they require a high-precision calibration (i.e., more accurate than usual)?
The description for CALIB_RATIONAL_MODEL says that the flag is not enabled for backwards compatibility reasons which apparently implies the flag should be preferably enabled by the users.