20 replies to this topic

[rhys1135]

Hi i own a D200 in aquatica housing.i have just bought a 17-70 sigma lens and will be using it in a 8 inch dome port,i was just thinking ,will i need a close up diopter for the lens or will it be ok on its own?if so has any one got any recommendations.thanks

[davichin]

Welcome Rhys! It will be ok on its own

[DiverPam]

Can someone explain Diopters? Just moved up to a D-SLR setup and keep seeing these mentioned alot in the postings on here. So much more to learn with SLR. I feel like I am back in school again - but this time it is FUN.

Thanks - DiverPam

[echeng]

Hey, DiverPam. Did a google search and came up with these informative articles on diopters:

http://www.earthboun...p-diopters.html
http://www.toledo-be...dex.asp?diopter

We use them underwater to focus on closer things -- sometimes, it is just to get the range of focus in far enough to focus on ANYTHING behind a dome port.

We also have a couple articles here on Wetpixel that talk about dome port optics... although, they are sort of technical.

http://wetpixel.com/...ll/dome-theory/
http://wetpixel.com/...-and-placement/

[Alex_Mustard]

I tried mine without a dioptre, with a single element dioptre (+3) and with a double element dioptre (Canon 500D). The pictures came out with all three set ups, but I prefered the performance with the single element dioptre.

Alex

[Marcelo Krause]

I used it with the D2x and Aquatica 8" port and port extension. Image quality was great. It focused on my hands on the dome. I liked the lens so much because of the versatility and different image perspective that it was one of the reasons for not changing to full frame during sometime.

By the way, Alex do you know if any lens has a similar performance on FX sensors?

Marcelo Krause
www.marcelokrause.com

[Alex_Mustard]

By the way, Alex do you know if any lens has a similar performance on FX sensors?

Unfortunately, no, Marcelo. And I too would love to hear about on that does. Any ideas, anyone?

I have been using a Sigma 28-70mm on FX as a replacement for the 17-70mm on DX, but it does not offer comparableclose focus, which is restrictive. Its a nice sharp lens that I have had from the F100 days. I have quizzed Sigma and they say that there is no direct FX replacement for the 17-70mm (regarding close focus repro-ratio) in their range.

Here are a couple of pictures from the 28-70mm on FX:





Alex

[Viz'art]

One lesser known impact of a diopter is the fact that a dome has a negative strenght (juliann post shows how to calculate it), so lets take a 8" dome that is a +/- minus 3 diopter power when immersed in water, that forces the lens behind to focus on a virtual images about 16'' from the sensor's position, if you add a plus 3 diopter to the lens you counteract this phenomenon this then rebalance you focusing scale,

In other word a subject shot through a dome give a virtual infinity image of about 16" from the sensor, therefore your lens has to be able to focus that close, put the +3 diopter and the virtual infinity image now appear close to where it should be on the focusing scale (infinity), what you gain in doing so is the possibillity to use some lenses that will not focus close normally and gain a much larger focus range, thus you are now able to do close focus wide angle photography, this is pretty useful when the lens does not have a macro capabillity like your Sigma 17-70mm does (Alex's 28-70 is an example of older wide angle that do not offer macro).

Also the smaller the dome port the more radical the phenomenom, yes Virginia, size does matter!

Understand that this is the rough cut method and there is a lot more data that can be pulled out of these equations.

FX still has some catching up in the field of interesting underwater optics, that makes me a DX boy for now.

[JackConnick]

Another way of adjusting it is to use an extension ring. That is how I shoot this lens, mostly to get the full lenght of the macro ability.

Jack

[Viz'art]

Another way of adjusting it is to use an extension ring. That is how I shoot this lens, mostly to get the full lenght of the macro ability.

Yes that also has an influence, our recommendation is based on the wide angle part of the lens, the part most likely to suffer from soft and stretched image edges due from poorly positionned dome, as the lens focal lenght get longer, the field of view become narrower and the edges sofness becomes less and less of a critical issue.

[Deep6]

Unfortunately, no, Marcelo. And I too would love to hear about on that does. Any ideas, anyone?

I have been using a Sigma 28-70mm on FX as a replacement for the 17-70mm on DX, but it does not offer comparableclose focus, which is restrictive. Its a nice sharp lens that I have had from the F100 days. I have quizzed Sigma and they say that there is no direct FX replacement for the 17-70mm (regarding close focus repro-ratio) in their range.
Alex

I have an older Sigma 28-80 f/3.5-5.6 "macro" 1:2 I used for the ole F4. Not wide enough for DX, IMHO.
Bob

Edited by Deep6, 20 August 2009 - 08:53 AM.

[Drew]

Ok the 17-70 has mfd of 20cm and the Sigma & Nikon 24-70 38cm. Won't a +6 or higher diopter compensate for the dome effect and get the mfd down? Sure it'll be like a 32mm lens by then. But it would work reasonably well no?

[davichin]

How about a 1.4x TC with the sigma 17-70 for FX? it should work as well as the tokina with 1.4x or 1.5x...

I tried it looking for a DX macro zoom and it focuses slow, but it focuses. Note that my lens is not the HSM one, so that one may work even better... Now, who with a FF camera will try first?

[rhys1135]

Hi i own a D200 in aquatica housing.i have just bought a 17-70 sigma lens and will be using it in a 8 inch dome port,i was just thinking ,will i need a close up diopter for the lens or will it be ok on its own?if so has any one got any recommendations.thanks

thanks for the info,guess i can start fireing away then?ill save the 50 quid i was going to spend on a diopter and put it towards my next dive trip.cheers

[DiverPam]

Hey, DiverPam. Did a google search and came up with these informative articles on diopters:

http://www.earthboun...p-diopters.html
http://www.toledo-be...dex.asp?diopter

We use them underwater to focus on closer things -- sometimes, it is just to get the range of focus in far enough to focus on ANYTHING behind a dome port.

We also have a couple articles here on Wetpixel that talk about dome port optics... although, they are sort of technical.

http://wetpixel.com/...ll/dome-theory/
http://wetpixel.com/...-and-placement/

Thank you for the information links on diopters. I am still trying to digest it all, but it is a little less foggy. - DiverPam

[davehicks]

I have the Sigma 17-70 HSM, a Nikon D300, and the Ikelite 8" dome port. I'm using the recommended extension ring for the lens. I did my first dive with this lens mounted last weekend, with pretty good results. I definately did see some softness on the edges in wide shots. I am not using a diopter.

The lens was pretty nice to use, and gives you access to a wide range of photo subjects if you don't know what you'll see. The Ikelite specs say that you can't use the HSM lens in the Ikelite housing, but you can. Just replace the standard plastic zoom clamp with a velcro strap. It's snug but the velcro catches on the zoom ring and works fine.

I'll link two photos, one wide and one macro.

Shot at 26mm: [notice some softness at the edges]


Shot at 70mm:

[JackConnick]

Does anyone know what S&S zoom gear fits the new HSM version of this lens? I'm thinking of setting it up in an RDX housing with the FE dome port. Since it's internal focusing now I don't think you'd really need an ext ring...?

Jack

[bankam]

I have the Sigma 17-70 HSM, a Nikon D300, and the Ikelite 8" dome port. I'm using the recommended extension ring for the lens. I did my first dive with this lens mounted last weekend, with pretty good results. I definately did see some softness on the edges in wide shots. I am not using a diopter.

The lens was pretty nice to use, and gives you access to a wide range of photo subjects if you don't know what you'll see. The Ikelite specs say that you can't use the HSM lens in the Ikelite housing, but you can. Just replace the standard plastic zoom clamp with a velcro strap. It's snug but the velcro catches on the zoom ring and works fine.

I'll link two photos, one wide and one macro.

Shot at 26mm: [notice some softness at the edges]


Shot at 70mm:

How do you attach the velcro to the lens, did you glue it on. I have been looking for an older non-HSM version of the lens but they seem to have disappeared.

[alanchungsf]

How do you attach the velcro to the lens, did you glue it on. I have been looking for an older non-HSM version of the lens but they seem to have disappeared.

I just saw that lens at 47th photo for the same price as the newer HSM version. http://www.47stphoto...availability=-1

Not sure if they've any in stock.

[davehicks]

Just wrap the velcro strip around once over the lens' zoom ring so there is about 1/2 inch overlap. The housing zoom ring collar will catch on the seam and extend the lens. Friction will be enough to pull it back. Just about as simple as it could be.

I just shot this setup again this weekend in Nanaimo and got some great images. I'm pretty happy with the 17-70 HSM.

Dave

I just saw that lens at 47th photo for the same price as the newer HSM version. http://www.47stphoto...availability=-1

Not sure if they've any in stock.