Is that just for when using it with a teleconverter or is it applicable to when using the 10-17 by itself?
To reiterate with my Subal ND30 (Nikon D300) housing with 4th generation port mount, Zen 100 mini dome port and Tokina 10-17, I need the 15mm subal extension ring which really places the Zen dome in the right place. Without it, attempting to zoom out to 17mm will cause the lens to come in contact with the port, not mention preventing the from reaching its full zoom range.
With the Tokina 10-17 and Kenko 1.4X Pro 300 Teleconverter, Grudge found the 33mm extension ring seems work fine. I have the 40mm extension ring, but as mention earlier I have not had a chance to test the combo in the water till I receive delivery a zoom gear that will work with that combo. I have however bench tested it and found that the lens did not experience any vignette, so right now looks like a strong contender.
Results may vary with Subal housings still using 3rd generation port mounts as they are slightly smaller in diameter.
