Another question about diopter for Sigma 17-70

I'm a long-time lurker here. There's a tremendous wealth of information offered by the forum users. Thank you everyone for so freely sharing your know-how.

I finally have a question. Or four...

I just bought the Sigma 17-70 (not the HSM version, but apparently the same diameter as HSM version). Will use it behind the Subal FE2 dome port.

I'd like to use the Canon 72mm 500D diopter, and Subal EXT-33 extension ring, and Subal 4ZNS62 zooming gear

> Is anyone using this configuration?

> The diopter looks quite thick -- is it likely to hit the dome?

> With the EXT-33 extension ring are you still able to zoom in as far as 70mm without hitting the dome?

> Is the Canon 500D a suitable diopter? I believe it is +2.

Thanks everyone

I just bought the Sigma 17-70 (not the HSM version, but apparently the same diameter as HSM version). Will use it behind the Subal FE2 dome port.

 

I'd like to use the Canon 72mm 500D diopter, and Subal EXT-33 extension ring, and Subal 4ZNS62 zooming gear

Is anyone using this configuration?

I am using this configuration for the most part. At any rate, it's close enough to answer your question. To be specific, I have the exact same lens (Sigma 17-70, not the HSM version) and dome port (Subal FE2). I am not using the Canon 500D diopter. I have the B&W +2 diopter instead.

The diopter looks quite thick -- is it likely to hit the dome?

I would answer a slightly qualified "yes". I brought my Sigma 17-70 to Grand Cayman in January. I had with me the EXT-33 extension and the B&W +2 diopter. When I attempted to use this combination, behind the Subal Dome Port, it seemed a bit too close for comfort. Alex Mustard, the workshop leader, took a look at it and suggested that it might be a safer idea to use it with the 40 extension instead of the 33. I just didn't want to experiment and risk scratching the dome port so I used the lens without the diopter for the week I was at the workshop. I am planning on getting a 40 extension so I can use the Sigma 17-70 with the diopter for my next dive trip.

With the EXT-33 extension ring are you still able to zoom in as far as 70mm without hitting the dome?

I never tried it with the diopter mounted on the lens. However, without the diopter I was able to zoom as far as 70mm without hitting the dome.

I wouldn't hesitate to zoom to 70mm if I had been using a longer port extension than the 33.

Is the Canon 500D a suitable diopter? I believe it is +2.

Although I haven't used it, I don't see why it wouldn't work just as well as the B&W +2 as long as the strength of the diopter is +2. As long as the filter size matches, it should be suitable.

Alex Mustard, one of Wetpixel's moderators, likes to use the Sigma 17-70 and is very knowledgable about its use for uw photography. You might also want to contact him if you have further questions.

Hope that helps,

Ellen

Thank you Ellen for the helpful information. I have emailed Subal about the EXT-40, but their offices are closed until April 20th. I think I will just get have to get the Canon diopter and the EXT-40 and hope for the best, because my dive trip is coming up soon...

I have used the Sigma 17-70mm with the 500D, a standard single element +3 dioptre and with no dioptre. My Sigma 17-70mm is the non-HSM, pre-stabilizer variety.

It works with all three. I did not do any objective testing - just tried different combos on different dives. I was happiest with the results from the single element +3 dioptre - so I continue using that for all my dives with the 17-70mm.

I miss that lens now I am on FX. In fact asked Sigma last week if they have or have plans for a FX (DG) lens that can match the 17-70mm. No was their answer.

Alex

Very helpful, thank you Alex. Are you using the EXT-33 or the EXT-40?