After doing such stuff myself all the time I had much fun observing somebody else doing it. Funny he missed those screws below the ring around the lens. I found that to be a typical location for such screws on many lenses, historical and new as well. Couldn't determine it from the video, but that "calibration device" might actually be a neutral density filter. At least it would be if this was a visible light camera :-) ... Thanks for doing this video and thanks for pointing it out. This was real fun !