Ports for EOS5D

Hi there at Ikelite,

I have decided to go UW from cropped to FF sensor, hence I recently bought a EOS5D Ikelite housing, which is going to replace my only 4 months old 400D Ike housing. I also need a longer macro lens like a 100m USM and need to find a replacement for the 10-17 Tokina WA.

Now I have Ikelite port questions for you :
- I own a 17-40L lens which I might intend to use UW. Ike provides two dome solutions either the 6" or the 8" dome : is there any significant image quality difference between the 2 for the specific 17-40 lens?
- I read that that the 6" dome cannot accept diopters with the 17-40 on a full frame camera.. is a diopter necessary for the 17-40?
- I could also buy a sigma 15 FE lens, do you have any 6" dome solution for it with the 5D -I must say I am a bit reluctant with the 8" because I travel quite a lot, hence the 6" is more convenient in that regard.
- I would like to use a canon 500D diopter with the 100mm Macro USM. does it fit in the port or do I have to switch to something else?

Thanks in advance for your answers

Cheers
Luko
(hoping you will have good news for the DS125 I have just sent to repair... )

The Canon 17-40mm lens focuses close enough to operate behind either a 6" or 8" dome port without the need of a diopter. "Significant difference" is subject to both interpretation and shooting scenario. In most instances especially with a camera 5D you will notice that the edges of your photos are sharper with the 8" dome.

If you want to use the Sigma 15mm FE I strongly recommend the 8" dome. You will have vignetting with a 6" dome and the 5D even if you remove the dome shade.

Usually the recommended flat ports leave at least 1/4" in front of the lens. Your best bet on the diopter is to stack it on your lens and measure the overall length from the camera body. Then make sure the port accommodates at least that length of a lens. Unlike dome ports and wide angle lenses, a slightly longer flat port should work fine even if you decide not to use the diopter in the future. See information on port lengths here:
Standard SLR Housing Ports

Regards,
Jean / Ikelite
IKELITE Underwater Systems