Tom Kline

FYI, I typically see a jump in the remaining battery power of one bar (on the unit's display) about an hour or so after ending a shoot (when I am home) and the housing is still cold to the touch even during the summer. This goes for both Li and Ni type batteries - cameras and strobes.

This is why I have mostly used gripped bodies here in Alaska: Nikon one-digit and Canon 1d models. Even with them I have had sudden death with the batteries (after a lot of shots).

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.

Thanks for the pointer Alex, I had to look it up!!! On the page above Fig 6.13 is point #4 (a list of the correction port properties): "4. The depth of field is increased about a factor of 2 over a plane port with the same camera lens and aperture." This sounds to me more a benefit of the de-magnification effect (1.33x eliminated) compared to a plane port. Mertens has a long discussion on depth of field and gets into loss of aperture due a plane port, compensating by changing distance, etc. There is also Fig. 6.17 that would be much better in color as there are 8 lines if I counted correctly. It would have been more interesting if Mertens had compared to a dome port as well. Based on the caption in Fig. 6.14 the examples of I-R port in the book (Fig. 6.13 same swimming pool) were shot with a 21mm Super-Angulon lens (made by Schneider for E. Leitz), f/4 and f/3.4 max aperture versions made by then; as well as M (Leica Rangefinder camera) and mirror lock-up versions (for the Leicaflex as the Leica SLRs were named back then)). These lenses are of the non-retrofocus type not too dissimilar to the 38mm lens your port was designed for.

I concur with your skepticism! In my experience focus is critical even with fisheye lenses which have a lot of DOF - (focusing evident because of focus breathing which is visible when changing pix quickly such as in the Lightroom "film strip"). Also interesting is that the port can do 120°!! This means that a 14mm should be possible. Main requirements seem to be the need for a front filter thread (so my old Nikon 14/2.8 lens is out) and a non-extending lens for either focus or zoom. He also answered my initial question which was related to the obvious modularity of the port.

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.

I wear fishing waders while doing most of my salmon photography!!! I try and wade in water that is below my knees in depth. This may require me to cross a stream several times going up and down stream to shooting sites. One has to learn a route for each stream. I have added weight to make some of my rigs a bit more stationary. I use polecam techniques while wearing waders. I have posted numerous examples of this here: https://www.salmonography.com/Salmonid-Topic/Photography-techniques/n-mnzBPB I may or may not have a hand on the camera pole! I mostly use fisheye lenses with a full range of dome sizes from superdome to macrodome. Lens focal length available in exif data on my website photos - click on the tiny i inside a tiny dot. I may have more than one housing with me with each configured differently. See: https://www.salmonography.com/Salmonid-Topic/Photography-techniques/n-mnzBPB/i-KS7Jjpz/A The pic title is somewhat tongue-in-cheek!

PPS. 5000 Euros plus taxes, shipping etc.

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

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.

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.

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.

Yes this is a problem but is highly variable and have to adjust my technique accordingly. I avoid using strobes altogether for many shots but they are done during daylight hours. Often have to make "a change in plan"!!!

I have loads of experience shooting Pacific salmon (all 5 species found in Alaska). In daylight as well as in the dark. I have used regular wavelength (halogen and LED) but small sized wide angle lights for focusing as well as for me to see after dark. Flashing has no effect. Salmon are very responsive, however, to shadows. Spooked when the moon rose behind me and I moved!! The technique is to keep everything still so the gear seems in inanimate to them. Best to sit rather than stand as well unless behind cover. I have examples of my shooting techniques here: https://www.salmonography.com/Salmonid-Topic/Photography-techniques

I caution about over-editing. For example I got into an argument with my agent's representative about the species identification of a juvenile salmonid fish. The select image for publication that my agent had was the esthetic champ from the series. The next shot however showed the anal fin of one of the fish splayed out so all rays could see. I did a cropped super blow-up of the anal fin and emailed it back to win my case. (The number of anal fin rays is an important characteristic for IDing salmonids). Non-savers can also be used for context such as location of shots. Rejects are also useful for posting on forums, ROTFL ...