Wider option for A7RII

Thanks very much! Really appreciate the response and clarification.

Just to follow-up – I was diving into port charts a bit more and see that the Zen 170 mm is also an option for the Canon 8-15 mm, although there doesn't seem to be much information on it here in the forum.

Does anyone have any experience with this port? I'm just trying to get my head around the options – I love the 100 mm Zen for travel friendliness, as well as being easy to snorkel with (I'm a whale shark researcher, so I spend a lot of time chasing them around), but it sounds like the 140 mm Nauticam or (potentially) the 170 mm Zen might be preferable quality-wise. Other than improved corners, do the larger ports have other benefits too?

A couple of considerations:

– I'd quite like the option of doing split-levels occasionally too, although perhaps I should just get a larger dome for those shots. Sounds like the 140 mm is still a little small for that, but 170 mm might be workable.

– I like to stay at f/8 when I'm shooting action whenever possible, as the A7rIII loses phase-detect AF in burst mode above that (it locks focus on the first frame). I haven't been unhappy with the Zen 100 mm, even with that restriction.

Best,

   Simon.

Thanks very much! Really appreciate the response and clarification.
Just to follow-up – I was diving into port charts a bit more and see that the Zen 170 mm is also an option for the Canon 8-15 mm, although there doesn't seem to be much information on it here in the forum.
Does anyone have any experience with this port? I'm just trying to get my head around the options – I love the 100 mm Zen for travel friendliness, as well as being easy to snorkel with (I'm a whale shark researcher, so I spend a lot of time chasing them around), but it sounds like the 140 mm Nauticam or (potentially) the 170 mm Zen might be preferable quality-wise. Other than improved corners, do the larger ports have other benefits too?
A couple of considerations:
– I'd quite like the option of doing split-levels occasionally too, although perhaps I should just get a larger dome for those shots. Sounds like the 140 mm is still a little small for that, but 170 mm might be workable.
– I like to stay at f/8 when I'm shooting action whenever possible, as the A7rIII loses phase-detect AF in burst mode above that (it locks focus on the first frame). I haven't been unhappy with the Zen 100 mm, even with that restriction.
Best,
   Simon.
 
 

Thanks very much! Geez I love this forum

Best,

   Simon.

The 140mm dome works perfectly with the 8-15 on the a7rii, Simon. I used that combo for a couple of years. Downside is splits are difficult, but for travel and currents,  it's a big asset to have the smaller port.

The 170mm dome is made for rectilinear lenses, just like the Nauticam 180mm. It's not the ideal option for a fisheye. 

I'd go with the 140mm + a seperate dome port dedicated for splits. The nauticam 8.5" acrylic dome works fine for that purpose and it's 1/4 the price of the 230mm glass dome

Thanks Andrei! That's definitely sounding like the best plan.

To add on Andrei point for splits it is true glass sheds water better but acrylic can be made work and actually you want your system to float as much as possible and a heavy dome is bad

I would also recommend 140+acrylic dome for splits the acrylic also gives you the rectilinear lens option with 16-35 mm

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Thanks again – definitely going with these options. Nice to be optimised for the task at hand. 

Loving this thread as i'm considering getting a housing for my A7R IV; all set for the macro front, just figuring out WA options ;-)

Couple questions:

1) How well does the Zen 100m work with the fisheye setup ? (I think Simon has some experience - do you have pics to share?) Also did you need to use extra extension on top of the N100->N120 35.5mm adapter?

2) Would the same setup (N100->N120 adapter + Zen 100mm) work for 28mm f/2 + Fisheye Converter? I'm considering that as it's lighter than the canon + metabones combow.

On 7/18/2019 at 10:20 PM, TimG said:

On the 230 dome port, if at all possible, Id suggest you take a physical look at the size of the port before deciding. I moved to a 230 port some years ago and was actually shocked when it arrived at just how big it was -

Hah! I am not alone.  I too was shocked when I saw my 230mm dome port.  I had never seen one before mine showed up with my first DSLR Nauticam rig.

Large domes give the most benefit for rectilinear lenses  this is all about having a larger radius virtual image for the lens to focus upon.  The relative difference in distance between the centre and edge of the virtual image is less for a larger radius dome which means the lens has a better chance of getting it all in focus within available depth of field.  The cause of soft corners in wide angle rectilinear shots is that they fall outside the depth of field.

A fisheye on the other hand is designed to render a circular view onto a flat sensor plane so the advantages of larger domes are less fisheye lenses.  What the fisheye does need is a 180° hemisphere dome so you can place the entrance pupil at the dome centre of curvature and still have 180° field of view without vignetting.  Bothe the 100mm Zen and 140mm Nauticam dome provide this as does the 4.33" acrylic Nauticam dome.