Panasonic 8-18mm, which dome?

This has been an interesting thread as I am looking at getting the Pana 8-18 for above water use and was curious as to how it would go underwater.

I currently shoot mainly macro with an Oly 60mm macro lens in a Nauticam housing plus a +10 diopter with Inon S2000 strobes which has been fine. Occasionally I do also a bit of CFWA with a Pana 8mm fisheye in a small dome port using the same strobes which are OK for CFWA work.

To do some serious WA stuff means a big capital outlay, as in addition to the AUD1200 lens, there is AUD1200 for the 7 inch dome port and zoom gear plus AUD1800 for a couple of Inon Z330 strobes. That's around AUD4200, whew!!

I think you should see the strobe upgrade as a separate step
The S2000 are great for macro and very close work but lack power for bigger scenes.
I would upgrade the strobes as a priority and leave the 8-18mm aside.
It’s an interesting lens but I would prioritise a 14-42mm and WWL-1 with a macro port more flexible option and easier to shoot.


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I am resurrecting this thread because I have finally obtained the technical details that I was after

Key facts:

1. Both the 7" acrylic dome and the 180mm glass dome have the same curvature radius so in terms of actual size there are no differences.

2. The 7" acrylic port has the centre of curvature 29.5 mm from the housing

3. The 180mm glass port with the 55 N120 N85 adapter and the 20mm extension ring has the centre of curvature 48 mm from the housing

4. The 8-18 entrance pupil at 8mm is around 38 mm from the housing

So in conclusion, once we remove the benefit of glass in terms of anti reflection and contrast in certain situations, both configurations are different from the ideal set up. Clearly the acrylic dome can't be adjusted as an 8.5 mm extension does not exist while the glass port could use a shorter extension of 10mm to position the dome in the ideal place.

There is however a post from @dreifish here that has used the 180mm with a 65mm extension saying that acrylic has an edge which does not seem to match any of the ideal considerations on dome positioning.

At the same time after speaking with nauticam they told me they use a macro slide to test MTF and the 75 mm length produces the best results. I do not have details on how they measure MTF and if they use corrected or uncorrected raw files however the 8-18 mm has a native barrel distortion of 6.2% according to optical limits and positioning the dome further away would introduce a pincushion distortion that would compensate the lens native barrel distortion and potentially result in a sharper image at expense of a reduced field of view.

In conclusion the improved sharpness of the glass would not have to do with the material being used but related to the different position of the dome. It has also to be said that the lens has less distortion at longer focal length and therefore there is a risk that pincushion distortion appears from a certain focal length on-wards that needs to be repaired in post and that the lens with the nauticam suggested extension does not perform consistently over the zoom range. Nauticam have confirmed they only test at wide end so this is plausible.

While it is not possible to extend the acrylic port of 8.5 mm it is possible to use a 17 mm mini extension together with a custom zoom gear (as the Nauticam one won't fit in the port) to bring the two ports at the same level of sharpness at 8 mm.

I am not convinced however that Nauticam approach is correct and I am inclined to suggest a shorter 10 mm extension on the port chart to let the lens perform as close as possible as it does on land and then do other adjustment to recover lost corner sharpness.

Hi,

I've bought the Pana Leica 8-18 lens with the 7" acrylic dome from Nauticam. It works very well as it was told above (that's why I ordered).

Thank you all for your feedback, it's very useful to know how a lens performs before buying.

I just want to point out something not very clear above about the lens size and the port :

• remove lens cap, and without the zoom ring, the lens can go through the dome without disassembling the dome from the housing
• with the zoom ring on the lens, it's too big to go through the housing and you have to remove the lens from the camera, the dome port from the housing, etc.

Not yet used for travelling, so preparing the housing from home it's not a big pain. On a dive trip, you have to be well organized.

For me, 1 battery last for 3 dives, so I think I can manage.

Now I've another problem : for split shots, I've got a lot of reflections inside the dome. It's a well known problem, and I would take any advice to find the best workaround. For the moment, adobe photoshop "fill content-aware" do the job, but this is not a long term solution :)

5 hours ago, rlamarche said:

Hi,

I've bought the Pana Leica 8-18 lens with the 7" acrylic dome from Nauticam. It works very well as it was told above (that's why I ordered).

Thank you all for your feedback, it's very useful to know how a lens performs before buying.

I just want to point out something not very clear above about the lens size and the port :

• remove lens cap, and without the zoom ring, the lens can go through the dome without disassembling the dome from the housing
• with the zoom ring on the lens, it's too big to go through the housing and you have to remove the lens from the camera, the dome port from the housing, etc.

Not yet used for travelling, so preparing the housing from home it's not a big pain. On a dive trip, you have to be well organized.

For me, 1 battery last for 3 dives, so I think I can manage.

Now I've another problem : for split shots, I've got a lot of reflections inside the dome. It's a well known problem, and I would take any advice to find the best workaround. For the moment, adobe photoshop "fill content-aware" do the job, but this is not a long term solution

 

Hi,

That's interesting, I don't have any trouble getting the camera/lens in and out of the housing with the dome attached?

Which zoom gear? I use a 3D printed one, not Nauticam.

Yes, internal refections can be a problem. I minimise it by painting parts of the lens with a matt-black artists paint (see my post above)

On 6/8/2020 at 4:06 AM, dave@immersed said:

Which zoom gear? I use a 3D printed one, not Nauticam

Hi, thank you for your reply. I use the recommended (from Nauticam) zoom gear : 36062 (https://www.nauticam.com/products/pl818-z-zoom-gear-for-panasonic-leica-dg-vario-elmarit-8-18mm-f-2-8-4-0-asph)

By the way it's a pity for me : I'm sure your 3D printed zoom gear was a more less expensive than mine, do you have the 3D model to print or any reseller ? It would be very grateful :)

On 6/8/2020 at 4:06 AM, dave@immersed said:

Yes, internal refections can be a problem. I minimise it by painting parts of the lens with a matt-black artists paint (see my post above)

Thanks for the advice, I found the post and will search the same kind of painting (https://wetpixel.com/forums/uploads/monthly_07_2019/post-78462-0-21700900-1562629417.jpg)

Any advice how to mask the front lens while painting ?

I think I've found it : https://www.deepshots.co.uk/collections/gears-for-olympus-and-panasonic/products/deepshots-panasonic-8-18-zoom-gear-new

14 hours ago, rlamarche said:

I think I've found it : https://www.deepshots.co.uk/collections/gears-for-olympus-and-panasonic/products/deepshots-panasonic-8-18-zoom-gear-new

Yes thats the one.

For the painting, I just used a very small artists brush and a steady hand, I managed to do it without getting any on the lens.

I gave 2 coats on the white lettering. It is a Matt Black paint, very non-reflective. It isn't perfect, but does reduce reflection.

Thanks @dave@immersed !

Here a short video of some rushes of this looong week-end (7 dives in 3.5 days) : 

I mainly made photos (some visibles in public on my FB profile https://www.facebook.com/romain.lamarche), but sometimes I want to use this "red" button

I really have to paint this lens, even in video underwater I see these numbers ...

Or buy the 180mm glass dome & adapter (~2000 € ..)

On 6/8/2020 at 4:06 AM, dave@immersed said:

Hi,

That's interesting, I don't have any trouble getting the camera/lens in and out of the housing with the dome attached?

Which zoom gear? I use a 3D printed one, not Nauticam.

Yes, internal refections can be a problem. I minimise it by painting parts of the lens with a matt-black artists paint (see my post above)

My bad, with the nauticam zoom gear it fits the N85 port. It's me doing it bad before.