luigi bertolotti Posted September 18, 2014 Share #21 Posted September 18, 2014 Advertisement (gone after registration) ..... Lastly, does the lens cover 35mm or is it for cine? ... Judging from the PDF file, is clearly for a Leica M body, which makes to think of 35mm coverage (even if Elcan made also "half format" 18x24 M bodies) Link to post Share on other sites More sharing options...
Advertisement Posted September 18, 2014 Posted September 18, 2014 Hi luigi bertolotti, Take a look here Elcan 21mm f/4 immersion lens. I'm sure you'll find what you were looking for!
pgk Posted September 18, 2014 Share #22 Posted September 18, 2014 Judging from the PDF file, is clearly for a Leica M body, which makes to think of 35mm coverage (even if Elcan made also "half format" 18x24 M bodies) I was thinking Leicina? It would make the optics far easier to sort out if that was a dome. Link to post Share on other sites More sharing options...
ph. Posted September 18, 2014 Share #23 Posted September 18, 2014 The Leicina Super has a very small film area, so it does not need a lens with dimensions that would cover a full frame. How about water filling as justified by avoiding the pressure differential that inevitably arise between the surface in contact with water and the air filled part ? p. Link to post Share on other sites More sharing options...
pgk Posted September 18, 2014 Share #24 Posted September 18, 2014 The Leicina Super has a very small film area, so it does not need a lens with dimensions that would cover a full frame. How about water filling as justified by avoiding the pressure differential that inevitably arise between the surface in contact with water and the air filled part ? If a dome ported lens, the large size is relative. I use a 200mm diameter Dome which still gives corner problems at times. Water pressure still applies itself somewhere! Link to post Share on other sites More sharing options...
luigi bertolotti Posted September 18, 2014 Share #25 Posted September 18, 2014 there is something not well clear if you compare the sketch of the PDF file (which, btw, clearly quotes the lens as "C251" and a coverage of 24x36) and the look of the item posted by the OP... The sketch looks such that the lens in itself has NOT the large domed front element... there are, apparently (left to right) : - Seawater - outside the submarine - A piano parallel window - part of the submarine's structure - The lens' assembly "attached" to this plain surface (in the text, they describe how this could be achieved - rather simply - indeed) - The cylindrical part of the lens with its interior filled with water (better to say "immersion fluid") , injected into from the inlet at side : this part is at all consistent with the lens' pictures. - Finally, the first glass element of the lens in itself... a small divergent element... I tend to suspect that the whole lens' schema in the sketch is drafted "semi-random"... with no strict adherence to the real lens' design... - Apparently, there is simply NO SPACE for the large domed front element of the depicted lens... it would interfere with the submarine's plain window... of course, there could be space for it with an appropriate mount to the window's glass : but in such case the whole brilliant idea explained in the document would fail : you had, before the film, a sequence of water (sea) - plain glass (window) - air (or void) - glass (large front element) - water (immersive fluid) - glass etc ("normal" lens' assembly) ; this is not consistent with ELCAN description ("..the space between the inner surface of the plano viewing port and the front surface of the lens is filled with a liquid...") So... there is SURELY a strict relation between the OP lens and the sketched project (and the "C251" is a proof of this) , but the lens in itself is not configured as prospected in the document... looking more like a lens maybe partially built (with the cylindrical body for fluid injection... surely a delicate component engineered just for this project) , but with a front element mounted for (maybe) testing it into a normal environment... Link to post Share on other sites More sharing options...
blankdl Posted September 18, 2014 Author Share #26 Posted September 18, 2014 As it stands the lens pictured has no sealing system visible so I cannot see how it could be used underwater. Perhaps the thread mounts it on to a sealing system or maybe the lens as it stands is incomplete. Its puzzling because, although the lens could well be designed for use with the front element in contact with water it clearly can't be sealed. Is there a sealing 'O' ring around the periphery of the front element/dome (may be visible as a thin black line if viewing from an acute angle)? If so I would suggest that it might be a prototype which could be used for testing by lowering it vertically into a tank of water until the front is in water contact (trapped air might be a problem though). ! There doesn't seem to be any possiblity of sealing around the exterior of the lens. However, there is adequate room for an O ring at the base of the threads and I can imagine a threaded flange (sort of like a toilet seat flange) that could screw into the lens to make it watertight and leave the external lens element exposed to water. Link to post Share on other sites More sharing options...
blankdl Posted September 18, 2014 Author Share #27 Posted September 18, 2014 Advertisement (gone after registration) There were a number of comments about testing this lens. Unfortunately, I do not own a Leica camera suitable for mounting this lens, so this issue will have to remain unresolved until later. In any case, I'm not inclined to perfuse the lens with liquid to test it, so any testing would be done in air alone which would provide some data but not all we might want to know. Several comments noted that this lens is rare. Does anyone have any idea who I might contact to establish the value of this lens? Link to post Share on other sites More sharing options...
jaapv Posted September 18, 2014 Share #28 Posted September 18, 2014 Westlicht. Link to post Share on other sites More sharing options...
luigi bertolotti Posted September 18, 2014 Share #29 Posted September 18, 2014 Ditto... and add the pdf page, of course. Link to post Share on other sites More sharing options...
blankdl Posted September 19, 2014 Author Share #30 Posted September 19, 2014 I don't mean to belabor the issue or prolong this thread, but it seems clear to me that the diagram in the Elcan pdf describing the lens doesn't work. It shows no structure between the immersion fluid and the porthole. It seems to me that you would need something to keep the immersion fluid inside the lens, therefore some optical structure on the outside of the lens. Furthermore, from looking at the lens I cannot tell how large is the chamber that holds the immersion fluid. It's possible that it might fill the chamber just beneath the outside dome lens that you see in the picture. Therefore, I don't put much stock in the accuracy of the schematic. I think it rather shows the general prinicple of the lens design. Note too that the pdf is not some slick advertising brochure for wide distribution but rather looks like something somebody just typed up, I'm afraid resolving some of these issues will require some testing and some time. Link to post Share on other sites More sharing options...
jaapv Posted September 19, 2014 Share #31 Posted September 19, 2014 Err.. The lens is designed to be used under water, so there is no need to contain the sea. Link to post Share on other sites More sharing options...
jaapv Posted September 19, 2014 Share #32 Posted September 19, 2014 This is not the only use of immersion lenses. In microscopy oil immersion lenses are used to cut out air refraction with high magnifications. A drop of oil is placed between the front element and the laboratory slide. Leica being originally a microscope company, it is not strange that they came up with this underwater solution. Link to post Share on other sites More sharing options...
pgk Posted September 19, 2014 Share #33 Posted September 19, 2014 It shows no structure between the immersion fluid and the porthole. It seems to me that you would need something to keep the immersion fluid inside the lens, therefore some optical structure on the outside of the lens. Furthermore, from looking at the lens I cannot tell how large is the chamber that holds the immersion fluid. It's possible that it might fill the chamber just beneath the outside dome lens that you see in the picture. Therefore, I don't put much stock in the accuracy of the schematic. I think it rather shows the general priniciple of the lens design. Note too that the pdf is not some slick advertising brochure for wide distribution but rather looks like something somebody just typed up,I'm afraid resolving some of these issues will require some testing and some time. The pdf states 'general schematic' and is, I suspect, intended to show the principle of how the optical system works rather than being an accurate and detailed drawing of a specific lens in actuality. In practice the lens would need fixing and sealing onto flat glass (be it in a submarine, ROV or whatever) and liquid introduced as shown - your lens appears quite different and I actually wonder if the engraving indicates a part from one of the Submersible lenses has been used in what might be a prototype, rather than being an accurate designation of what you have got? The dome on your lens is disconcerting because it means that whatever you have is either very heavily modified from the series of lenses shown in the pdf or is actually entirely different (my suspicion). If you find out more information please do post. You may be interested to read this: http://www.underseacameras.com/Underseacameras_Dome_Ports.html for a bit more background information. Link to post Share on other sites More sharing options...
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