Am thinking of using this lens with a canon 5d mkii hugyfot dome port and housing, anybody out there any experience with this combination, i.e does it work without the use of adding dioptres?
Malc

I'd be interested to hear anyone using this setup. I've seen stuff taken on this equipment so I know people use it. For my housing there's no requirement for a dioptre that I've been told about, was just told that it's not a good setup underwater.

Again, interested to hear people's response. The 24-70 rocks topside, such a great lens.

I like the focal lenght and range, so I tried the 24-70 in my Subal.

But in the Subal, the lens is so wide that you can't use a zoom gear. The housing gear goes right on the rubber covering of the zoom area on the lens. And since it's a telescoping zoom, rather than an internal zoom, like the16-35, it's just too hard to turn to make an effective zoom in the Subal.

At least, that was my experience.

I'm interested to hear how it might work out for you.

I too have tried this set-up with:
Canon 5D
Subal housing
Subal 8" dome and extension ring
+2 diopter, +3 diopter

Love the 24-70mm as a topside lens, and wanted the flexibility underwater. Like Gregarius stated, the 24-70mm is a really wide lens that doesn't fit comfortably in the Subal housing. I had the zoom ring affixed to the lens so it would work properly in the housing - prior to doing this, I would just shoot it with the lens fixed. I tried both the +2 and +3 diopters, and while some focal distances seemed sharper with one over the other, in the end, the +2's results were acceptable. However, to me, anything shot with a focal distance greater than 50mm was out of focus and not worth the time/effort to try to get a good shot. This set-up makes a full size rig gargantuan, and really heavy... getting this set-up slightly heavier than neutral (my preference) was a feat in itself, adding numerous Stix floats in different configurations. Until I'm able to either purchase another camera (crop sensor) or other lenses, this is a viable option in the meantime... it's just NOT an easy set-up. Good luck!

I don't know what the port hole dimensions for the hugyfot 5D2 housing is but on the Aquatica, Seacam and S&S, the 24-70 fits with no issues. It is actually slimmer than the 24-105 (but 1/3 heavier!). The issue with the 24-70 is that it reverse extends so it's at 24mm when fully extended. One has to have an extension of 70+mm (I can't really remember what I used) for the 24mm but have to be careful to avoid vignetting as the lens shrinks for 70mm. With an 210+mm (8"+) not so curved dome, it works well enough for the wide end (24-35mm) sans diopter or just a +1 diopter (but depends on your dome). However, because it reverse extends, one has to use a +2 or +3 diopter for the longer focal lengths.
Due to the reverse extension which makes finding the optimal extension difficult for the full focal range, plus it's a lot heavier, I suggest you look at the 24-105. I have both but now only travel with the 24-105. The image quality is better on the 24-70 if you look at it at 150% magnification. For lowlight, it can't be beat. For uw use, it's image quality doesn't offset enough of the issues you'd be dealing with fitting to a housing.