FYI
Here’s some calibration files done in Agisoft Metashape, when loading and processing images as [fisheye].
Resulting model as COLMAP output is THIN_PRISM_FISHEYE
MS_calibration_Fisheye_RIGHT3840.xml (456 Bytes)
cameras.txt (379 Bytes)
MS_calibration_Fisheye_LEFT3840.xml (459 Bytes)