Help choosing a wide lens for beginner

[pisauron]

You absolutely need a dome port - shooting 10mm through flat glass will produce very significant pincushion distortion and loss of AoV. Here is a sample pool shot, 10-18mm@10mm through a flat port:

View attachment 843004

And the same shot through a SeaFrogs 6-inch dome:

View attachment 843005

FWIW, I have SeaFrogs Salted Line 6-inch and 8-inch domes that I no longer use since I upgraded from a6300 to a6700 (different port mount), located in Rehovot.

That's pretty neat photos!

I see the Seafrogs housing has 2 dome ports: Optically correct & regular?

what's the difference? which one are you using here?

Thanks

 

[Barmaglot]

I see the Seafrogs housing has 2 dome ports: Optically correct & regular?

what's the difference? which one are you using here?

I'm not sure what you're referring to by 'optically correct'. They have wet dome ports that attach by 67mm threading to flat ports in order to affect in-water correction; these are made of acrylic only and come in 4-inch and 6-inch sizes. They also have dry dome ports that mount on the housing via their proprietary bayonet. These come in three mounts - they don't have specific marketing names, like, say, Nauticam N85/N100/N120, but they are differentiated by internal diameter, that being 80mm (used on the RX100 and A6xxx Salted Line housings, as well as the old Sony A7R II and Panasonic GH5 models), 90mm (used on all current plastic housings, including Sony a6600 and a6700), and 120mm (used on their metal housings). The dry ports come in a variety of built-in extensions, targeting different lenses. The 90mm and 120mm systems also have extension rings that you can buy, but the 80mm system doesn't. The 80mm system has domes in 4-inch, 6-inch and 8-inch sizes (although by my measurement, the 8-inch dome is closer to 170mm), with the 4-inch dome lacking any kind of extension and only available in acrylic, while 6-inch and 8-inch have a choice of acrylic and glass. The 90mm system only offers 6-inch and 8-inch domes, again, with a choice of acrylic or glass. The 120mm system offers 180mm and 230mm domes and only in glass - no acrylic. The domes have no built-in extension, but extension rings are available. There are no adapters/converters between the two systems, unless you make your own (I'm working on making one for the 4-inch dome to use with a Tokina 10-17mm on the a6700 housing).

The domes that I used for those test shots are 6-inch and 8-inch acrylic models with the A6xxx Salted Line housing and a6300 camera.

 

[pisauron]

I'm not sure what you're referring to by 'optically correct'. They have wet dome ports that attach by 67mm threading to flat ports in order to affect in-water correction; these are made of acrylic only and come in 4-inch and 6-inch sizes. They also have dry dome ports that mount on the housing via their proprietary bayonet. These come in three mounts - they don't have specific marketing names, like, say, Nauticam N85/N100/N120, but they are differentiated by internal diameter, that being 80mm (used on the RX100 and A6xxx Salted Line housings, as well as the old Sony A7R II and Panasonic GH5 models), 90mm (used on all current plastic housings, including Sony a6600 and a6700), and 120mm (used on their metal housings). The dry ports come in a variety of built-in extensions, targeting different lenses. The 90mm and 120mm systems also have extension rings that you can buy, but the 80mm system doesn't. The 80mm system has domes in 4-inch, 6-inch and 8-inch sizes (although by my measurement, the 8-inch dome is closer to 170mm), with the 4-inch dome lacking any kind of extension and only available in acrylic, while 6-inch and 8-inch have a choice of acrylic and glass. The 90mm system only offers 6-inch and 8-inch domes, again, with a choice of acrylic or glass. The 120mm system offers 180mm and 230mm domes and only in glass - no acrylic. The domes have no built-in extension, but extension rings are available. There are no adapters/converters between the two systems, unless you make your own (I'm working on making one for the 4-inch dome to use with a Tokina 10-17mm on the a6700 housing).

The domes that I used for those test shots are 6-inch and 8-inch acrylic models with the A6xxx Salted Line housing and a6300 camera.

I think i got it, i was referencing the difference between the acrylic & glass.

Both are 6 inch but one is "optical glass" and the other I guess acrylic.

I think I have the acrylic one at home I will have to check.

 

[Barmaglot]

You almost definitely have the acrylic; the glass ports are a relatively new addition.

 

[pisauron]

You almost definitely have the acrylic; the glass ports are a relatively new addition.

And the only difference between them is the material. There is nothing "Optical" that actually changes?

 

[Barmaglot]

And the only difference between them is the material. There is nothing "Optical" that actually changes?

I've seen a post from a Russian user who claimed that his glass dome is much clearer, but he didn't post any comparative samples, so it can very well be confirmation bias. In general, glass ports are heavier (more travel weight), less buoyant (don't need weights and/or require more floats), more resistant to scratches, but harder to impossible to polish if scratched.

 

[pisauron]

I've seen a post from a Russian user who claimed that his glass dome is much clearer, but he didn't post any comparative samples, so it can very well be confirmation bias. In general, glass ports are heavier (more travel weight), less buoyant (don't need weights and/or require more floats), more resistant to scratches, but harder to impossible to polish if scratched.

Thanks.

I have decided to purchase the new Sigma 10-18 f2.8 lens and use my 6'' dome port.
Seafrogs mentioned they are planning a zoom gear for the 10-18 sigma lens to be released soon.

 

[Pascale Lagarde]

I've seen a post from a Russian user who claimed that his glass dome is much clearer, but he didn't post any comparative samples, so it can very well be confirmation bias. In general, glass ports are heavier (more travel weight), less buoyant (don't need weights and/or require more floats), more resistant to scratches, but harder to impossible to polish if scratched.

I recently purchased the 6" glass dome (I already have the 6" acrylic dome). After several tests, no differences, distortions, light and even for split images, the only thing, as you said "more resistant to scratches, but more difficult or even impossible to polish in case of scratches", not a good point for me.