Tom Kline

I wrote it live so to speak but I did have to scroll up and down quite a bit to see the prev mssgs super keyboard challenged

somehow I screwed up and the text goes beyond the page!

Another data point: I have the book titled Free Diving by Rebikoff translated by Mervin Savill. Published in London 1955, first published in 1952 in French as Exploration Sous-Marine Ch. VII (the last one) is titled Underwater Photography and Filming. He writes a lot about his underwater flash units but not a peep about corrective optics Interesting that Ivanoff lived so long but what did he do from the 1960s onward? Searching his name I came up with a living artist. Another data point; See: https://www.spiedigitallibrary.org/conference-proceedings-of-spie/9192/91920P/Afocal-viewport-optics-for-underwater-imaging/10.1117/12.2061445.short Read the abstract!!! He calls them "the Ivanoff corrector lens" Lens is a bit vague since it can be one piece of glass or a whole unit like a camera lens, but for lack of a better English word lens has to be used (Abstracts often have a word limit (based on a lot of experience)). This is from 2014 so relatively recent. At Chris: the Nikonos opinion is from a current web page so would seem to be not too out of date but maybe limted to the experience of the author(s). I remember when the blue housings were released! It was during the 2 years my family lived in the US (Germany before and Japan after) when I bought the Hasselblad issue (house magazine) on it at a local camera store. This was between Sept 1970 and August 1972. So it is about 2 decades post Ivanoff earliest dates from the patent. BTW the first Hasselblad to use the 38mm lens was called the Supreme Wide Angle or SWA. The SLR was the 1000F. I have seen a SWA in person - it had a more primitive shutter. From the early 1950s. The SWC, the later camera, has to be used in the blue housing that takes the corrector lens. SWC/M and newer, no, because the tripod mounting shoe was moved to allow fitting of Polaroid backs.

Happy Thanksgiving! Thank you Alex. Not surprised that Zeiss may have made some improvements, but a doublet (2 elements glued together) for the port would also need to consider pressure resistance. How would hydrostatic pressure affect the glass at the contact surface between the elements? Lens element separation is bad enough in air (have seen Z optics with this problem - both camera and microscope). Thank you Adventurer. The 2003 article is interesting but may be misleading. It would be good to know how the author obtained the quoted material. It seems unlikely that it is from his memory if from 1968!! Rebikoff may have worked with JYC but it is Edgerton that JYC called Papa Flash. JYC is known to have had custom built underwater housings for his motion picture work. If Rebikoff worked with Ivanoff to invent the I-K lens per this article why is Rebikoff not in listed in the patent (other names (Grand and Cuvier) are)? Rebikoff may have outlived Ivanoff so had more of a chance to blow his horn (as well as being the book author). Also note the differences in the figure captions I previously posted. System Ivanoff in 1955 then called Rebikoff correction lenses in 1965! For the same items. R does show the smaller lens (actually two of them) on his stereocam. R may have built the cam but I more likely (his company or his associates) the lenses that are part of the housing. Thank you Davide. The Fathom unit seems to work more like the recent Sea&Sea correction lens as it is designed to work with a dome port but with 3 lenses elements so may be even more expensive. The S&S lens is aspherical and maybe it is doing the same job as 3 that are spherical. Thank you Chris. These lens were first developed by 1955 as that is the date of the earlier book and there are more examples in it. The patent was submitted in 1951 (in France apparently), received by USPO in 1952. Suggests a bit earlier than the 1960s.

I found a couple more links while searching the web: https://g6yb.com/g3ynh/photography/articles/wconv_intro.html Here is the important text: "Rebikoff-Ivanoff corrector, in its basic form, consists of a plano-concave front element with a magnifying element behind. It eliminates the optical distortion caused by a flat air-water boundary. The lens elements can be mounted in their own underwater housing, allowing the rear surface to be placed close to the flat port of an underwater camera housing. If the intervening water layer is thin, the external lens corrects for the distortion caused by the port." Interesting is that it can be used as a wet lens. How similar is this to existing wet lenses? Another is this: https://www.seafriends.org.nz/phgraph/film.htm Here is the important text: "Rebikoff-Ivanoff correction lens Demitri Rebikoff was one of the pioneers in underwater photographic equipment in the era 1940-1980. He designed an underwater correction lens that is also a wide angle converter, based on an inverted telescope. Because it does not change the camera's focus, it is said to be a-focal. As shown in the diagram, this correction lens consists of a negative lens as port and a flat positive lens placed 30mm further towards the camera. The lens can be put together from the parts supplied by a technician for eye glasses. It has a number of attractive advantages, not the least that it can be used both above and under water. It is also used as a 'wet-mate' underwater attachment. The Rebikoff 'port' is often used for underwater television cameras, but it is disappointing for still cameras, and cannot match the sharpness of the Nikonos lenses." Cutting and pasting brought in the figure. Note the change in order of the names for both sources. Was this arbitrary? Nikonos lenses are better???!!!!!!!

I second Davide! I am curious about: Rebikoff fronts glas uw correctors Ivanoff-Rebikoff corrector ports What is the difference and please provide citations? I ask because Rebikoff used inconsistent nomenclature in his books. I have his 1955 and 1965 books published in the US. They are very simmilar even using some of the same pix. See attachment. From what I know Ivanoff wrote the patent and Rebikoff actually built them. Apparently early in France and then in the US.

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 ...

This camera is clearly aimed at those for whom spending more is better. Now a hypothetical customer can boast about having a 61 megapixel camera!

Super transaction from member SH Jeong from this ad: https://waterpixels.net/forums/topic/2629-fs-seacam-240mm-super-dome-s45-g-pro-viewfinder/#comment-17499 Thank you! Tom

This contradicts the results in the link from post #2 - see 300th flash test.

Interesting thread with some great links, thanks!!! FWIW I just finished refreshing and analyzing (using a MAHA analyzer-charger) two sets of 8 Eneloop Pros that I bought in early 2023 from B&H (they were in 16 packs). (Reason for refresh: Adult salmon are expected in my target creek rather soon). Batteries last used in early Autumn 2024 (before major snow). The capacities (from the analysis) were mostly in the 2400 to 2500 range with just a couple above 2500. Not too bad for oldish batteries. (These are labeled as being made by Panasonic. Near the seam is stamped 22-xxxx. The four x characters are a bit challenging read but the 22- suggests they were made in 2022.) At the end of each cycle the batteries were barely warm to the touch. I felt them a few times during the test and at no time were they hot, just warm (like 100°F/40°C). Hot water out of the tap is much higher. The above anecdote about hot batteries suggest defective batteries or charger.