Adventurer

Good point, the patent was granted January 10th 1956 without mentioning the name Rebikoff. The reasons for that are highly speculative. However the Rebikoff / Cherney book you brought up called it "System Ivanoff" in 1955 according to you @Tom Kline as a trusted source. With that book being out prior to the patent and my other research that Rebikoff's Poodle ROV (dated approx. 1953–1954) had such or similar optical system mounted in front is an interesting circumstantial evidence of something I am not sure how to interpret. Rebikov and Cherney would have clearly exposed the US Patent US2730014A by Ivanoff et. al. to a prior art risk. This is a serious issue preventing any patent from being granted or after it has been granted preventing the owner from successfully enforcing or licensing it. This is also called risk of invalidating / novelty-destroying prior art or „risk of anticipation/obviousness in view of the prior art" -> meaning you cannot patent what's already out in the public domain. A book mentioning or prototype displayed on a trade show prior to filing is a common mistake by inventors for this. A comparable rule existed in the United States both in the 1960s (under the Patent Act of 1952, §§ 102/103) and already since the earliest patent statutes in the 18th and 19th centuries. As the patent also says "Filed Feb. 19, 1952" your book copy needs to be inspected more closely for the exact publication date and edition index. I would be interesting to learn if this book was actually the first edition or earlier publications are flying around. It might also be a potential reason why the image caption was renamed from Ivanoff to Rebikoff in a later edition. We do not know though, if this was done by Cherny, Rebikoff himself or some clerk at the publishing company. Seems not like that, .. contrary to what you wrote: Alexandre Ivanoff (1917–2003) outlived Dimitri Rebikoff (1921–1997). There are some Patents by Demitri Rebikoff online, his last filing looks like Oct. 31, 1990 for an optical diving mask restoring peripheral vision, citing the Ivanoff patent from 1956. No. Cannot be, as that patent is too recent for having been applied to my lens. As I initially wrote my Ivanoff-Rebikoff broadcast camera corrector front port is from "around the year 2000". I actually did not realise that it is an underwater corrector port for a long time, as IR corrector ports look very similar to obscure flat ports from the outside. You have to inspect them more thoroughly or "weight-lift" them to get the idea that they might be something different.

Yes, very rectilinear Davide. My optical glas may be a slight variant, though. As @Tom Kline asked for more historical quotations, I have found the following interesting recent writing from 2023, confirming the two-step process this optical system has gone through and what Alexandre Ivanoff's later role played in the 2-step invention. It's in fact the complex chromatic aberration correction lens element, that @Alex_Mustard had get measured and failed to reproduce with normal diopters. Have a read below... source: Photonics Focus Magazine: Article on Page 14 by By William G. Schulz

Maybe @Alex_Mustard can drop in an iphone picture of his glas element that is attached to his 20mm lens inside the housing and the front port element when the housing is dismantled. The two components are not hardwired to each other. The Rebikoff Element or Rebikoff optic is the part that touches the water and also seals the housing. It's not a simple flat port. The part that I named "Ivanoff" Element in the Ivanoff-Rebikoff System is what the joint venture of the two inventor brought new to the table in the early / mid 1960s.

Thank you @Tom Kline for this find. I have just ordered a copy of that old book and am exited. According to my research there are clear indications that Dimitri Rebikoff had already been working on water-contact corrective lenses before the joint “Ivanoff-Rebikoff” optics project. The classic Ivanoff-Rebikoff lens is more of a later, joint highlight—not the beginning of his work in optics. From what I know until now I cannot agree to your assumption that "Ivanoff wrote the patent and Rebikoff was the builder". Dimitri Rebikoff (1921–1997) started working on several underwater innovations in the early 1950s. One of them was Poodle ROV (approx. 1953–1954) Reports on the first civilian ROV, the “Poodle,” describe how Rebikoff placed a camera in a pressure-resistant housing and mounted a “water-corrected” or “water-correcting lens” in front of it in order to film Mediterranean wrecks at a depth of 700 ft. This is an explicit water-contact correction lens – decades before Nikon/Nauticam etc. took up something similar again, and long before he started his joint works with Ivanoff. An optics blog about “Air Lenses” writes that the classic Ivanoff-Rebikoff corrector system was “devised in 1960.” Modern photogrammetric works cite this optics as the Ivanoff-Rebikoff corrector, with references such as “Ivanoff and Cherney 1960, Rebikoff 1968.” This suggests that the first formal description of the optics appeared in scientific literature around 1960. Your later revision of the book (assuming the right book "saying System Ivanoff" is from 1965) would fit along well in this research and explain the photo caption inconsistency you found. It looks to me, that in both versions of the book the two illustrated lenses are not ment to be working on the same camera rig at the same time. They are two different Rebikov optics, without the contribution element that his collaboration with Ivanoff brought to life. The first photo I have found of a similar system that is illustrated on page 31 in your left book (as above written, I assume that is the older one) was used in his underwater scootering camera rig which you can still find in the diving hall of fame online today: source: SCUBA Diving Hall of Fame

Interesting! Could you clarify which of the two has more DOF ? Or better rank all three optical options, with best DOF from 1. 2. 3. top down?

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You should bring up the Insta360 AcePro2 on your radar. It‘s slightly more capable than the GoPro and the Osmo with the out of the box footage. Personally I use Insta360 AcePro (version1) as a small secondary cam and that one already smokes the other cams around. Due to the larger sensor and leica optics of the insta you already notice slight performance differences in the underwater optics. I have tested AOI, Backscatter and INON underwater action cam optics and found the INON image quality to be slightly superior than the others. There was also a thread here somewhere on the forums seconding my personal impressions about the superiority of the INON action camera optics.

Have you tried frame rates below 10 fps and above single shot mode ? That way you can rule out the general issue coming from camera or trigger. As you can see in the Henley Spiers strobe comparison photos: at 7 fps already the 2nd frame gets pretty dark and the RETRA is struggling at more open apertures.

I just recalled that Henley Spiers has shown the RETRA fast recycle time performance in his review: https://www.divephotoguide.com/underwater-photography-special-features/article/first-impressions-marelux-apollo-iii-2-0-strobe It‘s showing a lot of struggle at 7fps. The Marelux strobe smokes the oneUW and RETRA in this discipline.

10fps are done at easy with Marelux strobes at full power in their ultra-fast MTL mode. But you have to use them in MTL and with fibre optic cable (not Lumilink) to squeeze out the maximum repetitive performance. They are currently leading the fast recycle time without blackout frame technology in underwater strobes. Here on the forum is a pretty dismal measurement of mx strobe strength by dreifish though - something I could not agree to when comparing it 1to1 to my Backscatter HF-1. I can only assume the Apollo tested by Dreifish must have been a monday model or malfunctioning pre-production unit. On any AA eneloop powered strobe you will struggle to get fast recycle times near 8 - 12fps. You need a strobe which utilizes 18650 or 21700 high current discharge cells. Otherwise the capacitors cannot fill back up at the speed you desire.

Not an Ivanoff Optic but a Rebikoff Underwater correction port will also create a somewhat „virtual image“ similar to a dome. Contrary to dome port the corrective effect can already be seen in air, but the image is not improved in air.

Chris we have to stay sorted here, so everybody is on the same page and not mixing things up. There is no such thing as a sole Ivanoff optic working standalone and making your underwater image better. There is just Rebikoff-Ivanoff Optics, where the Ivanoff Element does Step two of the optical correction. Contrary to sole Ivanoff Optics, the Rebikoff corrector port can have a positive effect with increased IQ when used alone, simila but still different to a dome port. The Rebikoff corrector port will look very similar to a flat port when viewed from the outside, mounted on a housing. So for everybody going first time into this, there is: Flat Ports Domeports Rebikoff uw correction Ports Rebikoff-Ivanoff uw correction Ports

I would like to give everybody an update about my time and shooting experience with the above optic. Overall resumé : I am in deep love! The setup I am shooting with the Canon RF24-105 STM is a dream combination, filling the flexibility gap between my 8-15 Fisheye and the 100mm macro lens. Beeing able to shoot substantially wide dent Sharp reef scenes and fish portraits on a single dive with a full frame mirrorless system is amazing. However I would like to put some terms straight that may have been coined wrongly by the Keyword „Ivanoff Optik“ inspired by our dear Dr. Alex Mustard and who got me started researching and exploring this road. Alex was in fact shooting a Ivanoff-Rebikoff optic with 20mm fixed focal lengths, which is internet keyword wise sometimes just referred to as Ivanoff-corrector Port oder Ivanoff-Optic, leaving out the credits for Mr. Dimitri Rebikoff. During diving deeper into the topic, I found that I am actually shooting a Rebikoff optic, which goes without the correcting inner collection lens presented in their later introduced Ivanoff-Rebikoff design (sometimes referenced as IR design). All three approaches have their caviats. And as you have just read 3 instead of two, yes Rebikoff fronts glas uw correctors Ivanoff-Rebikoff corrector ports Dome ports ..share some commonalities in what’s possible concerning their optical limits. Most importantly the entrance pupil position problem cannot be thrown overboard with any of the above design. Furthermore they also benefit all from the same factors defined by the hosted dry air lens inside of them. The Ivanoff-Rebikoff design and Domeport have in common that they will extremely benefit from lenses that do not very much move the entrance pupil, most commonly found with fixed focal length. This explains also why Alex‘s IR-corrector port works splendid with a certain 20mm lens and created dismal results when trying to apply „the cure“ to other lenses. While everyone of you can easily work on optimal dome port position, you will very much likely fail in computing and manufacturing the exact Ivanoff Element for an Rebikoff-Ivanoff underwater corrector port and your lens; for the sake of beeing extremely costly. My suggestion for everyone is, if you are into exploring paths offside your dome port try to find large 2nd hand Rebikoff underwater corrector ports and start approximations with lenses from your camera brand, Nikon Z, Canon RF or Sony E-Mount. The latest UD elements and other 21st century master technology may help you to luck into a system that outperforms other optical underwater solutions you dived. For some extended reading about Rebikoff and Ivanoff .. their work and later collaboration I recommend these articles: https://blueexplorermag.com/2023/10/28/illuminate-the-abyss-the-innovative-inventions-of-dimitri-rebikoff-coloured-the-underwater-world/ https://spie.org/news/photonics-focus/julyaugust-2023/dimitri-rebikoff-pioneer-of-underwater-photography https://frogmanmuseum.free.fr/html/camerasandvideosrebikoffen.htm https://www.collection-appareils.fr/x/html/camera-5074-Alpa_U-Phot.html

I totally agree to your impression and did not understand why Seacam picked this particular difficult focal length to run their tests and first Ivanoff-Element (the part that screws onto the lens). It‘s worthwhile mentioning that a Rebikoff-Ivanoff optic will not be designed for zoom flexibility and you run into similar entrance pupil positioning issues as with wide angle zoom optics behind a dome port. The Ivanoff-Element is the part that will make your system afocal again and tries to get rid of chromatic abberations etc. The optical designers of the Ivanoff Element will have to make compromises in optimally correcting it for different zoom positions. When the lens is off these positions the underwater photographer will have to sacrifice IQ. As with Domeports and Watercontact Optics finding the right „Symbiosis lens designs“ from the topside lense choice will keep playing the critical role.

Nope. It‘s complete as it is and delivering dent sharp underwater images. All required optical elements are included in the main module. There is Ivanoff style and Ivanoff Rebikov designs, plus multiple variations derived from this principle.