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.