franMarz
commented
5 years ago Ok my bad, the aspect ratio is global and tied to the render resolution, so importing a new camera of any kind changes it every time. It's a shame that Blender doesn't natively support changing it per camera by now, though using linked scenes is somehow a workaround.
Importing a new fSpy camera messes up an existing fSpy camera, no parameters change in the old camera properties but the frame aspect ratio somehow changes to match the aspect ratio of new camera, even with the option "Update existing import" unchecked when importing the new camera.
The following images show how the old camera view changes and the model mismatch once a new fSpy camera is added to the scene.