Here my personal opinion to your points raised:
I am a bit confused. I read elsewhere that the difference in length was something on the order of 1mm, and that they should work with the same zoom gears and extensions.
It is in this post here: http://wetpixel.com/...topic=62734&hl=
I was the one who erroneously spread the rumor that the new Teleconverter is almost same length. I saw the physical total length in the specifications and confused it with the length it adds to the extension. Joss pointed out that in fact the extension differs by 7.8 mm (could well explain the worse performance and also might couse troubles with zoomgear)
"Also, you say above the 10-17 "quality is miserable" but I have always heard that although not up to 8-15 standards, most consider it quite good. Perhaps you were talking about land use? I generally don't pay much attention to how a lens does on land when i want it solely for dive use. It seems there is little connection between the two."
Yes, I was talking about land use. Underwater the difference becomes smaller (but of course a bad lens, what the Tokina is, will never become a gem), but with the teleconverter the problems become clearly visible on the small MFT sensor. When I use the Tokina with the 0.71x focal reducer (that also reduces the lens errors, see next point) the results are good - very good.
I also think that the Tokina 10-17mm was used first underwater and opened new possibilities of perspective. Later the Canon 8-15mm and the Nikon 8-15mm arrived, not to talk about the WACP and WWL-1. We are talking here about technical performance, not about photographical skills. Give a big shot like e.g.. Alex Mustard a camera obscura in a nylon bag and he still will win every competition, no matter what cameras/lenses the others are using. A bit of purple fringing and softness (Tokina) will not matter when the photo is outstanding...
"I was also under the impression that the recent full frame sensors actually revealed lens imperfections much more so than smaller sensors, not the other way around. Not arguing the point...just asking since I have heard it both ways."
Probably both condsiderations are valid. I use the small MFT sensor and can talk exclusively about adapting FF lens to MFT. The outstanding sharpness of FF is also achieved because the sensor is 384% bigger than MFT. The sensor heights are 24mm compared to 13mm. When the optical resoution of a lens is a certain number of lines/mm of sensor height, the optical resolution for MFT will decrease by a factor 13/24 (=0.54). Any optical errors will be multiplied by 24/13 (=1.84). Just simple physics, no way to get around it.
When the FF people moan that lens errors become worse because of higher pixels densities of contemporary sensors, one should add that a FF sensor with the same pixel density as the EM1-II (20Mpixel) should have 20*3.84 (= 76.8 Mpixel), a number that still has to be achieved by FF. So this fosters my view that smaller sensors require even better lenses than larger ones and explains why good MFT glass is so expensive...
"I have used micro 4/3 for several years and the Nikon stuff is new to me, so I have some learning to do :-)"
I followed your posts and know you had an EM1-II previously. I will be eager to read what you write in comparison about EM1-II and D500 (I started with MFT in 2017 and do not know the other camera systems)...
Edited by Architeuthis, 25 June 2019 - 11:09 AM.