Hi all

I see that Seacam has just launched tonight a new type of water contact optic seems it is designed to work with rectilinear lenses (16-35 range) and designed to give the same performance as in air. It uses an Ivanoff-Rebikoff lens system Called the Optical Precision Port it uses what looks like a relatively small flat port and a correction lens that is screwed in the front filter threads. Seems like it is very compact and travel friendly, though perhaps not particularly wallet friendly. Here is a link to their website, scroll down and click on the link "12 month practical test for some more details on the optics." A friend of mine Don Silcock did the field testing.

https://www.seacam.com/de/optical-precision-port/

Believe Zeiss many years ago developed something similar for the UW hassleblad system.

Since I will be attending the DEMA Show in Orlando Florida this week I will be sure to swing by the Seacam booth to have a look (provided they bring one) at this new lens to see what it is all about.

Looks like a very clever design: https://www.seacam.com/en/optical-precision-port/#6910ccd3bd523-4

It is modular making transport a bit easier. Part of it is a dedicated large diameter (providing buoyancy) port extension. Seacam could build alternates to accommodate other lenses. Ask them about this at DEMA.

On 11/7/2025 at 3:31 AM, Chris Ross said:

SNIP

Believe Zeiss many years ago developed something similar for the UW hassleblad system.

Correct! Alex Mustard has this and wrote about it some years ago after having it modified for his Subal housings. It was originally designed for the Superwide camera that had a fixed 38mm lens for the 6x6cm format so had a 90° angle of view. A bit narrower than what Seacam has come up with. As well the internal lens was for the Hasselblad series 63 filter size (same as series VIII, threading on internal lens same as filter retaining ring), quite a bit smaller than the corresponding part for the OPP.

What an irony 🫢🤣 I am diving my Ivanoff Optic now for 6 month at a fraction of the costs and with more corner sharpness I observe in the sample images on the Seacam page and in the teaser. But I am sure Seacam users will buy this anyway.

Glad to see some general progress and competition in the underwater optics field again.

I'm happy to see some innovation from Seacam here. Although I'm not sure it's for me - I've been happy with the 16-35 PZ and compact port, and corner sharpness hasn't been an major issue except at CFWA.

Couple of things I'm curious about:

1. Is the field of view of the lenses the same as on land?

2. Which of the major lenses are compatible? Can we use say a 24-105?

3. What's the weight - they say "similar to the superdome" which is 2950g. The compact port is 1850g.

4. What are the dimensions, weight, prices, diameters of the optical correction lenses? The one shown at the page is 77mm, but Sony's 16-35 are either 82mm (GM/GMII) or 72mm (PZ/Vario-Tessar). Canon is 82 or 77 and Nikon 77mm. I'm sure they've thought about this.

Doesn't sound travel friendly if those weights are correct...

Seacam did a live post on Instagram where some of these details are revealed (can still be watched). Weight is 2.9 kg but is compact if one dismantles it. Stuff can go inside the empty port extension. The two optical parts are flat so a bit like oversized hockey pucks - the larger one, the front port is about 18cm in diameter but only 4 cm thick without the shade, 6cm with. Thus far only lenses with a 77mm filter size but I would not be surprised if an 82mm version might be on the horizon. The Nikon 16-35 is fairly long so a shorter, squatter port extension might be in the future for other lenses. Hence my question above.

PS. I suspect mainly lenses that keep a fixed length will have to be used.

PPS. 5000 Euros plus taxes, shipping etc.

11 hours ago, Adventurer said:

What an irony 🫢🤣 I am diving my Ivanoff Optic now for 6 month at a fraction of the costs and with more corner sharpness I observe in the sample images on the Seacam page and in the teaser. But I am sure Seacam users will buy this anyway.

Glad to see some general progress and competition in the underwater optics field again.

Pleeeeaaase show the Ivanoff-solution?

36 minutes ago, fruehaufsteher2 said:

Pleeeeaaase show the Ivanoff-solution?

I did quite a while ago in this forum.

It is very funny how similar it looks to the new Seacam solution. However it‘s noteworthy that I can use mine without a 2nd component on the lens:

Thread name:

Ivanoff Style underwater corrector port on a Canon Marelux MX-R6II

Edited yesterday at 08:40 AM1 day by Adventurer

Found!

Thanks a lot

Thanks for posting the link to the previous thread which I had missed. I looked up the references in that thread. Note that the description in the Ivanoff patent indicates two lenses named 1 and 1'. Shown as well in the figures (but a and b in Fig 5). If your Ivanoff port does not contain both of these lenses it is incomplete. Lens 1 (or a) is the replacement for a dome port but only curved on the inner surface, the front surface being flat. To accommodate the curvature the front port is thick at the edge is hence a negative lens. The correction lens (1' or b) is a negative lens, thicker in the middle.

Edited 2 minutes ago2 min by Tom Kline