I've got a 5503 ikelite port that fits the sigma 15mm fisheye, 18-55mm canon kit lens, and 35mm F2.0 prime lens. I haven't tried yet but expect the 50mm F1.8 will fit as well but it will need a diopter or 12mm extension tube.

My other port is the 5505.45 which is specially targeted to the Canon 100mm macro lens. I was looking for a fast zoom lens to fill the focal range between my 35mm and 100mm prime lenses and was hoping it could use the 100mm macro port. One candidate is the Tamron 28-75mm F2.8. On ikelite's Canon port chart the 5503.80 dome port is recommended for this lens. That port is for lenses less than 5". Because the 100mm macro lens port is for lenses less than 5.1" I assumed it would fit and my main worry, and possibly the reason for Ike to recommend a dome port, was vignetting at the 28mm setting of the zoom lens.
I'm pleased to report that the lens fits the 5505.45 just perfectly. Fully extended at the 75mm setting there is just a small gap left (the lens is 5" fully extended) and at 28mm the lens is 3.6" long and at least on a 1.6x crop sensor there is no vignetting due to the port. I expect you'll be fine on a 1.5x crop nikon camera as well, but perhaps not on a FF Canon 5D.

I personally prefer a flat port over a dome port because you don't have to worry about needing a diopter (the minimum focus distance is 33cm which is borderline for a 6" dome port) and I consider the extra 30% magnification due to refraction at the flat port surface an advantage. On a 1.6x crop sensor 28mm is effectively the equivalent of 45mm on a FF sensor so there is really no need for the dome. Another big advantage is that I don't have to buy and, especially, lug around yet another port.

The standard ikelite zoom clamp fits barely around the 2.9" wide lens barrel and if you have to put it on and take it off repeatedly you are either going to scratch the lens or damage the zoom clamp. So I strongly recommend you get the larger diameter zoom clamp which fits perfectly, even without adding a rubber adaptor strip. This clamp has been shipped with housings for some while and you can get it separately if you don't have a spare one.

The competition for this Tamron lens are the 24-70mm F2.8 from Canon and Sigma, but both are too wide to fit in ikelite ports. The canon 28-105mm F3.5-F4.5 has a good reputation and offers great value for money. Subadru has shown excellent results with that lens underwater. However, at 28mm the lens is only 3" long and I fear vignetting may start to become a problem (Ike recommends the 5503.55 dome port for this lens, suggesting it stays shorter than 4.5" at 105mm). The extra 30mm at the tele end of this lens is nice and it has a ultrasonic focus motor. However, it can't focus closer than 50cm (max magnification is about 1:5.2) and it is a slower lens.

The most similar competitors are sigma 28-70mm F2.8 lenses. There seem to be two of them, an EX DF and an EX DG model, and I'm a bit confused about what's what. The EX DF model appears to be older, extends from 4" @28mm to 5 1/16" at 70mm and may just barely fit in the 100mm macro port. However, this lens doesn't get very good reviews, especially at the tele end of the focal range. The current version is the EX DG model that is 3.4" @28mm and about 4.4" at 70mm. I could not easily find reviews for this model. This lens will definately fit in the 100mm macro port but the shorter 3.4" @28mm has a bit more risk of vignetting and some of your working distance will be wasted on space inside the port. Ike does not list this lens in the port chart but I assume the optimal port will be the 5503.55 dome port or 5505 flat port (both are for lenses less than 4.5" long).

Both the Tamron and Sigma EX DG lenses are 2.9" wide and have a 33cm minimum focus. The Tamron has 5mm extra at the tele end and this extra reach and the longer physical size of the lens give it a maximum magnification of 1:3.9 compared to 1:4.4 for the sigma. More importantly, all reviews I could find for the Tamron lens indicate that it has very good optical and build quality. The lens sure feels solid but it is too early to comment on the optical quality. I'm going to use is underwater next month and will report later in January once I'm back. As I said I didn't find good reviews on the sigma EX DG but I may not have looked hard enough. I believe Alex has had good results with the 28-70mm from Sigma, don't know which model, but he always seems to get good results

Bart


PS: Here are some reviews in case you are interested in a lens in this focal range.

http://www.the-digital-picture.com/Reviews...ens-Review.aspx

http://photo.net/equipment/tamron/28_75_Di/ (Bob Atkins: compares with Canon 50mm F1.8 and 28-135mm IS)

http://www.popphoto.com/assets/download/8212003124116.pdf popular photography PDF tamron

http://www.popphoto.com/assets/download/311200313351.pdf popular photography PDF sigma EX DF

This is the lens that's on my 5D most of the time. It's a great walk-around lens for a FF. It'll probably make a good fish lens. I've been meaning to try it. It's not supported by Aquatica, but I played around trying to make it work with my old Sigma 105 focus ring. I think it'll zoom with a little duct tape engineering.

Before getting that lens you might want to read these reviews:

http://www.the-digital-picture.com/Reviews...ens-Review.aspx

http://www.fredmiranda.com/reviews/showpro...t=43&page=1

Have you considered the 17-50mm Tamron?

http://www.the-digital-picture.com/Reviews...ens-Review.aspx

Aloha!
JCD

Hi "J",

Yes I like the FredMiranda site. Sometimes you get a few "this $100 lens isn't as good as the $1000 lens I used to have" complainers but if you read a decent number of opinions you get a good feel of what to expect of a lens. I definitely looked at the Tamron 17-50mm F2.8 but so far I find I'm using wide angles the least and so far I'm happy with my cheapo 18-55mm Canon kit lens. Just stop it down to F11 and it's doing fine for my needs. I would be interested to read about other users experience with the Tamron 17-50mm, it seems to do very well topside and has a nice short focus. I bet the new Sigma 18-50mm F2.8 "macro" is going to be good too. Their initial 18-50mm F2.8 attempt didn't fair too well so I expect they will make sure this time that they are at least as good as the Tamron.

Bart