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I found this crazy Rodenstock XR-Heligon 50mm 0.75 Lens on eBay.

I have some questions:

  • what kind of mount does it have?
  • how does one change the aperture? I see no aperture ring...
  • is there a way to modify it or use some adapter so that it works on a modern Nikon FX DSLR?
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  • From experience, eBay links vanish in a few months. Do you have a different reference you could use? – mattdm Jan 28 '15 at 13:47
  • From a random experiment I did: Adding a biconcave element (one I found in the junk box) seems to lengthen the registration distance a bit (not enough though) ... now I don't know enough optical theory to say which (preferrably commercially available) concave lens would work better here... maybe someone here does? – rackandboneman Sep 20 '18 at 0:19
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There are a number of fast X-Ray lenses out there. Rayxr De Oude Delft 50mm f/0.75, Rodenstock XR-Heligon 50mm f/0.75, Precise Optics 50mm f/0.75, Varo Optical 50mm f/0.75, Leitz 65mm f./0.75. There are also a number of longer f/0.95 – f/1 lenses in the 90mm range from the same lens manufacturers.

There's a company Miyazaki R&D (well, it's just one man hand-modifying the lenses, not really a company) that has successfully converted the De Oude Delft 50mm f/0.75 to Leica M-Mount so that it can be used "normally: ie. not macro only, but all of these lenses are still fixed focal length, fixed focus, and fixed aperture. They will only be useful for mirrorless cameras with short registrations and best with a camera that has live view. Also be aware that the lens conversion isn't cheap.

These lenses have seen a jump in price from about $200-$1000 depending on the condition and maker. Rodenstock and Leitz typically command a higher price because they are well known in the optics game. We all know that Leica/Leitz lenses have been the 35mm film standard forever and Rodenstock made the best large format camera and enlarger lenses.

I hope this clarifies most of the questions about these super-fast X-Ray lenses.

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This article on Daifuku Sensei gives a good overview of the Rodenstock lenses. Summarising the most important points:

  • Not only is there no aperture ring, there's no focusing ring either.
  • They're designed for a registration distance of just 7mm (compare that to the ~45 mm of SLRs or ~20mm of micro 4/3s), so they're never going to focus to infinity.
  • Daifuku Sensei suggests one way of attaching them to an SLR - get some extension tubes and then physically glue the lens to the extension tubes.
  • Extreme field curvature and chromatic aberration.

But it's still f/0.75 :-) It's also worth noting that the author of that post picked up his lens for $20 5 years ago, so you may get a better deal by looking around.

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  • Thank you so much, this is a great tip. Indeed I would be scared to attach anything like this directly to my D600. – az1mov Jan 27 '15 at 22:45
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I think that the approach of using these lenses with 35mm cameras, digital or film, via adapters or improvised shutters, with possibly ND filters used as a misdirected substitute for aperture control (doesn't really do that, for the depth of field would not change just because the ND filter is in place) is wrong-headed.

I believe that the best use of these lenses is with alternative media cameras that have a very low ISO equivalency, that is, require long exposures, and even when used in the field are on medium format or large format cameras, possibly of the user's own construction. With the very long exposure time for some of the obsolete, now home-crafted media, one can use a shutter as primitive as the old movie house dowsers, basically a gate that securely shuts of light to the lens or from the lens.

I have two such lenses. They appear to be internally very clean, with lens faces in fine condition, although both were filthy with accumulated dust, due to my brother's careless storage conditions. Wish I knew where he got them... perhaps from Berkeley, CA camera club decades ago? Both are made by the same Japanese company, but do not identify the manufacturer. I have offered one on eBay, but may not renew my listing, for I think I might dismantle it and insert a fixed aperture ring to give it some depth of field. Both are 150mm, are identical with greater than 120mm front lens element, and, if I recall correctly, greater than 90mm rear element. They are also labeled 9X. I was considering that they possibly could be used in IR realm, for they seem to lack conventional coatings.

I saw one of these listed on the Web a couple of years ago, and not for sale. The listing was old and I didn't pursue the question of what to do with it. I'd reiterate that these are not really good candidates for the 35mm camera, unless you want to use it in a studio setup for special purposes. I think you'd need at least a doublet correction lens in an adapter tube to get your image to your 35mm camera's image plane. If you're bound and determined to mount this to a 35mm camera, consider setting up a makeshift lens bench and measuring your distance from rear lens element to image plane. Use a low wattage filament lamp, such as those 2W to 5W decorative clear (unfrosted) lamps, perhaps a clear candelabra lamp as your object. Project onto a white card. Measure the distance. Perhaps you recall doing something like that in high school physics class or middle school general science class?

If you have one of these, or seek one of these for your entertainment, be prepared to do more work than merely attaching an F-mount, K-mount, or whatever camera mount adapter you think you need for your camera... it'll take some measuring and planning.

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