Hi all. I'm back from my first trip to land of Newbie-to-WA Flaildom, and it was actually pretty fun! The lighting and exposure were easy! (Who knew that Tv mode with strobes on TTL works perfectly in most situations???) So I had a lot of fun, and got a lot of pleasing shots.

Except I didn't love the mega mega mega smeary corners I got with my lense/port/camera combo. Clearly a bad combination, which I'd like to remedy!

Does anybody actually use this lense on this camera in an Ike housing without smeary corners? If so, would ya mind sharing what port/diopter combo you're using? FWIW, I don't really care about the wide end on this lense - I like the 35-40mm end better and could sacrifice the lower end if necessary (and save hooking up the dang zoom gear every time I change the card or battery ).

Thanks in advance!
Susan

PS - I don't trust the recommendations on the Ike website because those produced the completely unusable smeary corners I'm getting now, in a 6" dome that doesn't leave room for a diopter. I'd rather find somebody who is actually making this combination work and do what they're doing.

Hmm... The Ikelite website recommends a 6" dome and no diopter for the 17-40L? That doesn't sound right.

You need an 8" dome w/ the proper extension and try shooting with a +2 diopter. This lens just has soft corners at low f-stop - even above water. I use it a lot, but I make sure to shoot at F8 or above.

Cheers
James

They say a diopter isn't necessary, since the lense focuses quite close. Or they did back when I bought this combo (from a well thought of source who frequents this board).

So do you use the 8" dome and a +2 diopter then? I'm happy to incur any corner unsharpness that's native to the lense, I just don't want to add any more unsharpness with the port.

Thanks,
Susan

Frankly, I'm surprised you can use that combo. When you are underwater diving with the camera, how close can your subject be? A diopter isn't necessary when using this lens w/ a large port, but some people recommend one. When shooting with a small port, I'd say the diopter is mandatory.

Christa Loustalot recently had the same experience as you - she was shooting the 17-40L with the Athena dome and had terrible corner performance. She added a 77mm Canon 500D diopter and that helped a lot.

A diopter will not add softness to the corners - they just don't add that kind of distortion. They can add CA and some pincushion distortion, but not dramatic softness.

I'd recommend you get the 8" port, or else a 500D diopter (about $120)

Cheers
James

The problem is that if I use a diopter, I have to get another port, because there isn't a spare millimeter in this 6" dome, I tried. Grr. And the 8" dome is $$$. But then, a different lense and proper port for it will also be $$$.

Sorry if I implied the diopter would add softness - I meant the port itself.

Susan

I shoot with a 5d and 16-35mm. I got smeary corners with the 6" dome and no diopter combo. I bought a 8" dome port for this lens and the corner sharpness is much improved!!!

First post here in a long time (and as all my registration stuff needed to be redone, it will probably be post 1 all over again...) Don't see anything in a search, although it seems this must have been asked before...

Have a Canon 20D in an Ike housing that I've been shooting with a flat port and Canon 100 mm macro. Like that combo but wanted to add a wide angle setup for an upcoming trip. Have a 17-40 EF L Canon lens and went with a 5503.51 port as described in the Ike charts. I actually ended up calling Ikelite as this port is listed as a Tokina- or somesuch-specific port but they confirmed it is the right one. During that call I also enquired about the comment in the charts that says a +2 may improve edge sharpness and was told that yes, it might, and yes, it would fit in that port.

Just assembled all the new goodies without the +2 and it all looks good. But, it really looks like there is no way the extra quarter-inch or so of the +2 mounting ring has room to fit behind the port, and as the +2 has a fairly rough milled front surface I'm super-reluctant to try to fit the port with the filter in place as it looks like it will scratch the heck out of the port. Plus, if it doesn't actually gouge a big scratch on the inside of the port, the wide metal mounting ring on the +2 looks like it will stop the lens from seeing most of the dome port. Figured I'd ask around before I give up on the +2 altogether or try it and ruin something. Has anyone used this combination?

BTW, I went with the Hoya +2 which seems to have quite a wide mounting ring, although as these things are stackable I'd guess any +2's mounting ring would have to be slightly wider than the dome of the glass itself.

Leaving Saturday, so any quick suggestions or fixes hugely appreciated.

Bob

Hi. I've posted this one before in a similar thread. I use a 5D in ikelite housing with the 17-40 and a +2 diopter, with 8" dome.



I've found this combination gives me acceptable sharpness.

Bob- I havn't tried it with the port you have, but maybe if you temporarily put a piece of cloth or something over the front of the diopter to stop scratches you could (very gently) try fitting it in the port.

Cheers
Fergus

Thanks Fergus,

After I posted last night I did something similar to your suggestion - stuck a thin strip of post-it note on the side of the lens and then progressively trimmed it back until I could mount the port without it bending. Looks like there's only about half the thickness of the filter ring space, so all the Ike literature that says use that port with a +2 is less than accurate. Expensive mistake if I'm going to see really soft edges.

Bob.

Just got off the phone with Ikelite tech support. As usual their response was super customer-oriented, helpful, and, well 'supportive.'

They told me they'll look into the +2 situation with that port and change the literature if their findings bear out my experience. They did point out that there may be lower-profile +2s that fit OK and said they'd make me a custom port that would fit my lens and +2 if I wanted to go that route.

Re-reading stuff here it seems the 8" would have been the way to go and I guess having different length ports to put behind the dome gives you a lot more options. When I was trying to decide, the extra cost and the paranoia of having yet another seal pushed me to the 6". Maybe I'll have a dome for sale in a few weeks

The 8" is backordered at the moment, so there's nothing I can do before this trip, but I wanted to post a thumbs-up for Ikelite's folks.

Bob.

Thanks for posting that, Bob. I think we just have to bite the bullet and get the 8" dome (and I'm going to get a different lense too I think). Glad to hear Ikelite folks were receptive to your comments.

Susan, et al.,

One other thing I discussed with the Ike representative was trimming the filter as it looked like there was plenty of room for the glass and functional part of the mounting ring but just not enough room for the part of the ring designed to accommodate stacking a second close-up filter in front of it. So I figured "what the hey?" and risked destroying my $40 piece of hoya glass...

I'm in "panic packing" mode right now (the usual weeks worth of work that needs to be completed before I leave Saturday) but I took the filter apart and an hour or so with a jeweler's saw and some files and matt-black paint saw it trimmed it back to something that fits with room to spare (at least a mm or two ).

While I'm away I'll try to get some similar-subject with and without the +2 shots and if all goes well I'll report back here in a couple of weeks with some example shots and (if it works) pics of the filter-trimming.

One other thing that I should have figured out from the diagrams etc on Ike's site, but that escaped me until they were pointed out during that conversation so I'll reiterate them here: a WA zoom may only have a limited range of focal length that will work with a particular front-element to dome combination. Stopping it down to get more DOF obviously helps, but at some point I'm sure strobe power will become the overriding factor (less of an issue with the macro setup I'm used to, so this will be an interesting trip).

Bob.

If the front of your 17-40L is almost touching the inside of the dome (this lens does not change length when zooming) that is just way too close! From my testing, I found that somewhere around 35mm of extension is needed with the Seacam dome. Are you sure you are using the right amount of extension????

Cheers
James

Hey James,

Don't know if you remember me, but I was (one of?) the first to connect and say 'Hi' when you had your first live chat session way back in the CP5k days (I was in Utah then and excited about moving to Maine)... Anyway, things proved you to be absolutely right.

The short answer: Despite using exactly the port that Ike recommends for this lens, with no +2 filter the edges are really soft. Adding the +2, in my hands, leaves the lens often unable to get a sharp autofocus, and even then when the center of the field is sharp, the edges still seem very soft.

The longer answer: With the Hoya closup filters, it was clear there was insufficient room in the port for lens plus filter. Using thin strips of post-it notes stuck to the front of the lens barrel I figured there was enough room for the +2 glass, just not the threaded front section of the mounting ring so I cut that off with a jeweler's saw, smoothed and matt-black-painted the fresh cut, and guesstimated there is about 1/32 inch of space between the back surface of the port and the front of that +2. If anyone wants details of cutting back a filter, PM or email me at bobs at artisananimal.com.

On a weeklong liveaboard (carib explorer 1 run by explorer ventures from Georgetosn Bahamas, BTW, 100% thumbs up on that crew) I did dive 1 in shutter priority at 1/125 with no close up and intentionally shot some gorgonians and other stuff that had edge features. Dive 2 did the same with the +2 close up. Then went back to my 100mm macro for the rest of the day. When I looked at everything that evening, I found unhappy edge shgarpness and critical focus as described above.

Day 2 did the same thing but in manual mode. Stuck with 1/125 but stopped down from the typical almost-wide-open lens that shutter priority chooses to F10 or smaller. Regardless of the +2, the edges were better (predictably) at much smaller apertures. For some subjects stopping down to F18 gave me decent sharpness but at the cost of having to bring back +/- 2 stops from the raw conversion with all the crap that that introduces. BTW I have a DS125 and a DS50 for fill, and much below F10 at any "reasonable" distance this combo just doesn't throw enough light. (although wihh my macro when I'm not concerned about getting correct background exposure etc. I can usually stop down pretty well and get an image that's +/- correctly exposed with decent DOF).

Most of my test shots were set a little off of the lens's widest setting (i.e aiming for about 22mm) although subjectively I don't believe there's much difference between wide and zoom in what I saw, although the Ike rep pointed out there will be a "best" focal length for the curvature of the dome with any given zoom lens.

All in all, big thumbs down to the recommended port for the Canon 17-40 zoom. I really think the recommended port for this lens is poorly considered and/or inappropriately advised -- or at least requires some more detailed notes on Ike's port-selector chart!. Sure, of you're shooring a pic of a shark and want the eye and face in focus the soft edges won't be a turnoff (I took just such a shot), but for "underwater scenics" the sharpness just's isn't there (got my share of those too!).

An aside here. The Ike rep said he'd work with me when I got back on potentially upgrading to an 8" dome. (Kudos Ike; and I hope they follow through on their assertion they'd reevaluate this lens/port/diopter combo.) Sadly in the very last surface interval of the trip I found a reg dumped in the camera wash and on all my final dive pics I have a nice haze spot corresponding to a visible ding in the port. Better dig out that thread on fixing scratched domes!

Next trip I think I'm going to try the remachined Canon Kit Lens and 6" port that came with the housing and camera when I bought it (Ken, BTW, if you see this, I think I lost your email address - drop me a line!). But in all likelihood when the piggy bank is sufficiently re-fattened an 8' dome and _sensibly_ selected port will be in the cards. Adivce here anyone...?

Hope this is of interest or helps someone...

Bob.

Hi Bob,

The 17-40L is not that great a wide angle lens to begin with - so don't be too hard on Ikelite. Even shooting topside you will see edge softness.

For that reason, the bigger the dome the better. When I have to use the 17-40L (because I need a zoom) I use a dome w/ a 9" chord diameter and an even larger radius.

When I want a decent 17mm lens I shoot the Tokina 17mm

Cheers
James

Hi James.
I think that's a little bit of an unfair statement - topside, the 17-40 lense is
as sharp as any zoom - sharper than most. Sure, it's not as sharp as a prime,
but that's the nature of the beast.

The sharpness problems we're complaining about here are due to the dome
curvature and physics and dimensions and whatnot - the lense itself is fine topside.

That said, however, I have to say, I am DONE trying to use this lense underwater!

Even some of the samples people have posted using the 8" dome to me have
unacceptable corner smearing. If I do shoot more wide angle in the future that has corner detail, I'll be
getting a FE or something and a compatible port that is a tested and proven combination.
(I.e., I'll be copying what somebody else has already made work!)
No more of this "Well, I already have this lense, so let's try and make it work." LOL, bad
idea!

Happy shooting.
Taxgeek/Susan