Canon 8-15 + Kenko 1.4x Dome and extension port

I'm planning to start using a Canon 8-15 + kenko 1.4x in a Canon full frame camera, I would like to know what's the port extension I need for an Aquatica Housing and 8" dome. I've been looking to the Aquatica port chart but I can't find it. Is anybody using this combination who can advise me please?

10 hours ago, atus said:

I'm planning to start using a Canon 8-15 + kenko 1.4x in a Canon full frame camera, I would like to know what's the port extension I need for an Aquatica Housing and 8" dome. I've been looking to the Aquatica port chart but I can't find it. Is anybody using this combination who can advise me please?

here's the port chart:  https://www.aquatica.ca/en/charts/canon_type_4.pdf

It does not list that combination, however no problem you just need to add extension equal to the thickness between flanges of the 1.4x you use.  I believe the Kenkos are 20mm thick.  Aquatica have a 0.8"extension (21.5mm) and the bare lens takes one of those so on that basis you would need 21.5 + 20 = 41.5mm extension to have the same as the bare lens. 

So you could use 2x 0.8" rings (43mm)  or a single 1.56"- 39.5mm which is either 1.5mm more or 2mm less  extension than calculated.   You might want to check for vignetting even if is only 1.5 mm more  extension if you go with 2 x 0.8"ring option- it's probably OK particularly as you are reducing maximum field of view and probably only using the 15 - 21mm range anyway.  (below 15mm the lens does not fill the 35mm frame)

You could also use the 16.5mm plus 25.5mm rings for 42mm extension.

11 hours ago, ChrisRoss said:

It does not list that combination, however no problem you just need to add extension equal to the thickness between flanges of the 1.4x you use.  I believe the Kenkos are 20mm thick. 

Yep, I use a 20mm EXR when using a Kenko 1.4TC. Works fine.

Thank you very much to both, you have really been very helpfull !!!

Are Canon 1.4 extenders incompatible with the Canon 8-15?

2 hours ago, JWNZ said:

Are Canon 1.4 extenders incompatible with the Canon 8-15?

yes- correct, they won't fit due to the protruding element up front.  They only fit lenses designed to accommodate them, which includes super teles and some of the macro lenses.

Thanks Chris