how to calibrate the response function and vignetting factor

[hjf579068]

Hi, @ NikolausDemmel
Firstly，thanks for your great work, and I recently want to calibrate the response function and vignetting factor of my own camera. So I capture a sequence of image with my own camera and then calibrate the response and vignetting factor with your code(batch mode). However, the response and vignetting factor always changes. As far as I know, as the increase of backend optimization times, the response and vignetting factor should be stable. And can you give me some advice about calibrating the response and vignetting factor? It will be a great honour to get your reply.