Canon FF, EF 17-40/4L and diopters - is it possible?

I use Canon 5D with EF 17-40/4 L behind Ikelites 8 inch dome. However, corner sharpness is really not very good, to say the least . It seems pretty clear that at least part of the answer to the lack of corner sharpness is to use a diopter, and, as far as I understand, the Canon 500D diopter should do the jobb. The problem is that above water, using skylight filters on the 17-40 on ff requires special slim filters in order to get rid of vignetting. Does anyone know if it is possible to use the 500D (which is about one cm thick) on the 17-40 underwater without adding horrrible amounts of vignetting, or is there any other diopter brand that works for the canon ff, 17-40 (or 16-35) and 8 inch dome?

Regards

Bent

Let me go check. BBIAB

James

Here's a sample at F8 - 17mm with the 500D

Looks like some very slight vignetting.

Let me go check. BBIAB

James

 

Here's a sample at F8 - 17mm with the 500D

 

Looks like some very slight vignetting.

Thanks a lot, James. That is much less than I anticipated and probably easy to correct in post. Do you use the 500D on the 17-40 under water, and if so, what are your experiences with the setup?

Regards

Bent

Hi,

I think that the 500D is better suited to lenses with a longer focal length really. I use it on the Tamron 70-200 f2.8 for macro and it is excellent. I'd probably use a B&W +2 diopter w/ the 17-40L

Cheers

James

I posted a comment in another thread that using dual element dioptres for wide angle lens correction behind domes may not be as good as single element dioptres.

Using dioptres to correct the negative lens effect of a dome in water has two advantages. First the a dioptre allows the full range of the lens's focus to be used when focusing on the virtual image created by the dome. The second advantage perhaps helps corner sharpness more. A dome creates a virtual image that is curved. The reason for soft corners is that the corners of this virtual image are too close to the lens to be in focus (as lenses are designed to focus on a flat plane, not a curved one). A single element dioptre fortuitously creates a slightly curved plane of focus and thus helps the lens focus on more of the virtual image created by the dome.

AFAIK, one of the features of a double element dioptre, like the 500D, is that it does not curve the focal plane as much as a cheapy single element dioptre. This is advantageous for macro photography, but for use behind a dome you loose the second factor mentioned above.

I have not done detailed tests of this, so this is theoretical musings, rather than tried and tested knowledge. I have tried the 500D behind a dome and it was OK, but the corners were not great - however I was using a very small dome, so it was not a fair test.

Alex

Hi,

 

I think that the 500D is better suited to lenses with a longer focal length really. I use it on the Tamron 70-200 f2.8 for macro and it is excellent. I'd probably use a B&W +2 diopter w/ the 17-40L

 

Cheers

James

I am a total newbee to diopters. What would be the difference in performance between the B+W and the Canon 500D? After Googling them, the B+W seems a lot slimmer, but besides that.

Bent

Edit: Sorry, didn´t see Alex answer above before I wrote my question. It answers it in full. So I guess I will try both, the B+W for the 17-40 and the 500D for underwater macro. And, of course, I can then also compare both with the 17-40 and the dome !

Thanks a lot for helping me out here.

I can then also compare both with the 17-40 and the dome

I have now ordered both, the B+W for the 17-40 and the 200D for the EF 100 macro. I will, however, not be able to compare them on the 17-40, as the macro and the 17-40 are of quite different thread sizes! Reality struck!!!

Thanks a lot for the information I got in this thread. It really clarified a lot of current wisdom on diopter use to me. I look forward to test the 17-40 behind the 8'' dome on my next trip, it might be a usable combination after all.

regards

Bent C

To add to what Alex said, a primary reason for dual element diopters like the 500D is to provide correction for chromatic aberrations. Wide angle perspectives are unlikely to show CA introduced by a diopter. Macro lenses can.

I am a total newbee to diopters. What would be the difference in performance between the B+W and the Canon 500D? After Googling them, the B+W seems a lot slimmer, but besides that.

 

Bent

 

Edit: Sorry, didn´t see Alex answer above before I wrote my question. It answers it in full. So I guess I will try both, the B+W for the 17-40 and the 500D for underwater macro. And, of course, I can then also compare both with the 17-40 and the dome !

 

Thanks a lot for helping me out here.

I have been using the 17-40L with a Canon 30D for general UW photos with an Ikelite case and dome. What is the experience with the diopters for close up use? I have an upcoming trip to Borneo and was hoping not to have buy another lens and dome for close up and near macro use.

rick meinig

co springs

Hi, I´m also using a 5D in a Aquatica with a 17-40 and 100mm (a Sigma 15mm aswell). Never felt the need for extension tubes and diopters, but I was thinking of what I have been missing.

My main objective would be to improve corner sharpness and alow a closer fucusing for my 17-40.

As for the macro, just whant more maginification (the 100mm gets a bit short on FF with tiny things).

Any advice in what I shoul use for them both?

Thanks, N.

How about a 1.4x or 2x teleconverter? Since the focus knob is on the macro port for the Aquatica housing, all you'll need to buy is a longer extension ring.

Cheers

James

I use a 500D Canon diopter for smaller stuff with my 5D and Aquatica Housing. I have just started experimenting with a 25mm extension tube as well, will let you know the u/w results. For my 17-40 I use a +4 B+W diopter and it has improved the corner sharpness considerably.

Hope this helps

Tristan

My reference here is the Nikon 17-55mm, Nexus housing w/FP170 dome, but same fix may apply to Canon 17-40. I determined that I needed a +4 diopter for corner sharpness. However with the lens zoomed out all the way with diopter, it made contact with surface of dome. Since there was about 3/16" of diopter mounting ring protruding beyond the element, I made a simple wood jig to hold the ring (with glass removed) while I sawed off about 1/8" of excess material, then cleaned up with file. Put some black magic marker on bare aluminum edge to prevent glare. Problem solved.

I came back from a months trip to Borneo a couple of days ago. I used the 17-40 with the diopter for a number of Sipadan dives. Last year I did the same trip using the 17-40 without dipter. As far as I can see on the pictures I have looked at till now there is a very marked improvement in corner sharpness with the diopter. They are not perfect with the diopter, but mostly usable, which is far from the result without the diopter.

/Bent C

Thank you all, great help!

James - What brand 1.4x or 2x teleconverters are you talking about? I have the canon 1.4 but it is not compatible with my 100mm 2.8?

Tristan - Excellent, I will order a +4 B+W diopter for the 17-40. Was also thinking of the 500D for macro, folowing Alex Mustards adivice and using a single element dioptre for wide and a dual element dioptre for macro. But what kind of extension tube will you be trying? And did your 17-40 lose any angle when wide open (17mm) with the diopter?

Bent - Where you using the +4 B+W diopter aswell?

All the best, Nuno.

Sigma or Tamron. The Tamron Teleplus is very good and very popular.

Cheers

James

Bent - Where you using the +4 B+W diopter aswell?

 

 

All the best, Nuno.

No, I used the 2x diopter.

/B

Thanks James,

I never tried non canon teleconverters, but have read great reviews about, Kenko, Tamron and Sigmas, seems they are good qualitie and are compatible with more lens than canon. By the way, you meant Kenko Teleplus, and not Tamron, right?

I am thinking maybe a teleconverter will do the job, does anyone know if Auto focus still works o.k. with a a 1.4 or even 2x Kenko TC, on a 100mm 2.8? If it works like canon´s it should work o.k. till F/5.6, so they should both maintaine AF.

Thanks, N

Thanks James,

 

I never tried non canon teleconverters, but have read great reviews about, Kenko, Tamron and Sigmas, seems they are good qualitie and are compatible with more lens than canon. By the way, you meant Kenko Teleplus, and not Tamron, right?

 

I am thinking maybe a teleconverter will do the job, does anyone know if Auto focus still works o.k. with a a 1.4 or even 2x Kenko TC, on a 100mm 2.8? If it works like canon´s it should work o.k. till F/5.6, so they should both maintaine AF.

 

 

Thanks, N

Auto focus still works with both converters. However, going down to more than 1:1 ratios of enlargement, my experience is that AF is very hard to get to lock. I have set AF to the thumb buton and ususally with high enlargements more or less exclusively use manual focus anyway. Setting AF to the thumb button makes it possible to use AF if required, and still have the advantage of MF for high enlargements.

/Bent

I have the canon 1.4 but it is not compatible with my 100mm 2.8?

What about using your Canon TC with the 12mm Canon extension tube?