Tokina 10-17 on Canon 5D in Subal Housing

I'm just about to buy a Tokina 10-17 to use on my 5D body & Subal Housing. I have the FE2 dome port (2005 model). The Subal site tells me that I need an 18mm extension to use with this lens. My questions are:

1. I have a Subal 20mm extension (which I use with my 24mm lens), am I right in guessing the 20mm extension will be OK. It seems a bit crazy to spend a lot of $$ when there's only 2mm difference.

2. I already have a Canon Extender 1.4 EF mark 2 - can I use this behind the 10-17? And if I do, how do I use the gear ring on the 10-17? How can I change focal length on the lens? Or should I just pre-set it when it goes into the housing and leave it at that? And if so, is it better at the wide end or towards the 17mm?

3. If I'm using the Extender on the lens, will the Subal 50mm Extension be OK to use behind the dome port (as I already have one of those also)

I'll appreciate any thoughts/ideas/advice

thanks

Carol

Carol

The Tokina 10-17 will not work with the Canon 1.4TCs. The Canons have a protruding lens element that will hit the rear glass of the Tokina, you are better off to use a Kenko, Tamron or Sigma TC. I believe the Kenko and Tamron are identical, just different badging.

The Lens will vignette at the 10mm setting with the 5D. You will have to zoom in to past 11mm to avoid black corners. As the Tokina is meant for use with APS-C Cameras, that's to be expected

The 50mm extension would be too long for your application, you may want to try the setup with just the FE2 port as the Tokina will still focus to the port with a TC.

Good Luck!

S