On 11/7/2025 at 1:31 PM, Chris Ross said:

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.

Is it just me or does the demo image look not so impressive?

having talked to seacam at DEMA, i think a few things weren't made clear in their preview. The lens is not a water contact optic like the WACP. It is water corrector port. According to seacam it is designed to allow a land lens to perform exactly the same underwater as it does on land, so the image quality seems largely dependent on the optic you put behind the port. Not all lenses are created equal so I imagine it will take some experimentation before the ideal lenses to use are determined

8 hours ago, Chris Ross said:

and 424mm in air. Here is the reference, scroll down to section 4.

https://pmc.ncbi.nlm.nih.gov/articles/PMC4732081/

Without doing a detailed analysis, it's basically guesswork

Thanks heaps for the reference!

I'm digesting it... while I enjoy reading about other systems, it's how to get the best from domes that interests me most, since I already own them and mine are smaller and lighter than the fascinating Seacam optics.

Great find and read Chris! A 33% increase seems valid. I suspect it is more noticeable when DOF is somewhat greater. For example if DOF is 100mm, 133 mm might be noticeable. However if DOF is just 1 mm, 1.33 might not seem like much of an improvement.

Having a look at Seacam’s new Optical Precision Port (OPP) at DEMA, the size and weight of the show’s sample model (built for Nikon’s F mount AF-S 16-35mm) overall is much lighter than Nauticam’s WACP and FCP ports. The flat front on its own has a similar weight range as one of Seacam’s macro ports. The extension port is made of Delrin which is lighter than aluminum. The internal optical that screws in the filter thread (72mm, 77mm & 82mm will be the three primary thread sizes available) of your wide-angle prime or wide-angle zoom in the 16-35mm range weighs about the same as a Nuaticam SMC super macro lens. The extension ring for the front port will be provided in different lengths based on the wide-angle lens you are using with the OPP’s internal correction lens. For example, if your wide-angle happens to be something like Sony’s E-mount FE 16-25mm f/2.8 G Lens or FE PZ 16-35mm f/4 G Lens, the OPP’s overall assembled weight and size will be less than that of a 180mm to 230mm domeport with an extension.

6 hours ago, Walt Stearns said:

For example, if your wide-angle happens to be something like Sony’s E-mount FE 16-25mm f/2.8 G Lens or FE PZ 16-35mm f/4 G Lens, the OPP’s overall assembled weight and size will be less than that of a 180mm to 230mm domeport with an extension.

I think there is still a fair weight advantage to a dome with the 16-25 lens.

Some weights (kitchen scales):

Nauticam 180 dome 1183g. N 140 dome 668g. N100-120 35 adap 313g. N100-120 25 adap 183g. N120 35 ext II 267g.

I have tested the lens with both domes:

140 + 25 adap + 35 ext = 1118g.

180 + 35 adap + 35 ext = 1763g.

Surprisingly, there is no discernible difference in central IQ between both domes, with f11 giving good sharpness into the corners (sharp across a 30mm circle, viewed at 100%).