Ikelite/RebelXT - 6" or 8" dome?

Hi again. I'm about to pick up an Ikelite housing for my Rebel XT. I will mostly be using the Canon 17-40 f/4L lens, but I'm not sure whether it would be better to get the 6" dome port, or the 8" dome. The 6" is obviously less expensive and easier to pack for travel than the 8". But is there an image quality advantage with the 8" for a 17-40 mm range lens?

Thanks in advance.

I suspect you haven't had replies to this because few people are using that lens underwater?

FWIW,

I have both the 8" and 6" dome for my EF-S 10-22 and I also have a 6 inch dome for the kit lens, 18-55mm.

My experience is that there is image improvement using the 8" dome in preference to the 6 inch, with the EF-S 10-22.

I took the 18-55mm for two dives in its 6" dome and decided I'd never dive with it again, very difficult to get a focus lock in that port.

3 weeks ago, I decided to take the 18-55 lens for a run in the 8 inch dome (#5510.81), in much the same conditions as the previous dives (4 metre milky viz) .

That combination was great.

All of the shots at this link are with the 18-55, all from 2 shore dives here in Sydney during May,

http://www.aengusm.com/images/Day%20and%20...%20Dives/May06/

I'm not familiar with your lens so its your call but FWIW, thats my experience.

Cheers,

Aengus

<_< With the Rebel camera the multiplier effect on the 17-40 L lens is like a 27-64 mm lens, not a very useful lens for underwater. I would say that using the same lens with a full frame camera would allow you to see the benefit of that lens and its quality. I would recommend the 10-22mm lens in the 8" port unless you really plan on getting one of the full framed Canons in the near future. I use the 17-40 L lens quite a bit on land with my film (Canon 1V) camera and on my 20D and it is a very nice lens in the proper situation. Just another opinion.