Canon 8-15mm fisheye and teleconverters in Photography Gear and Technique Posted September 28, 2020 · Edited September 28, 2020 by Marsh Yes, I agree, you are correct in your assessments. I almost bought a 140mm from a friend, as it's a premier glass dome with coatings, no doubt a beautiful port. I use the 4.33 port over the 140mm due to my grafting a 67mm swing mount onto it's shades. It simply allows me the ability to use all the lens I prior mentioned with the one port, something I can't do with the 140mm. Besides, I had this swing mount set-up on my N85 4.33, so it was rather easy switching it over to the same size N120 4.33. As much as I wanted the 140mm, i determined it too difficult to re-engineer my custom swing mount to it's shades. These were the main reasons I stayed with the 4.33. It had nothing to do with weight or size. I would like to add to the original questions regarding the post topic: While focus is accurate using the Kenko 1.4 (mine is a blue dot) and Metabones IV combination (latest FW even in low light) I noticed I often have to hit the focus button twice to get an accurate focus (as defined by Peak Focus highlights) for some reason? The 1st push sometimes knocks it out and the 2nd brings it back in focus? It's quite consistent and might have something to do with the firmware on the MB? It mostly seems to happen when I'm not doing CFWA. I haven't tested whether this happens with the C10-18 by itself. I also haven't tried it using the AE/AF/MF back button as my focus activation button, rather than the half shutter standard method, which is how I want my Nauticam a6500 housing set up. As soon as I get a chance to set up the back button focus method, I'll update the post, along with some underwater tests.