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Thread: Lens element sources and specs?

  1. #1
    Drew Bedo's Avatar
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    Lens element sources and specs?

    Many old brass lenses look great but have really bad glass elements. Others have shootable glass but the metal parts look like an artifact from Pompeii.

    The early Petzval lenses are a pretty simple formula that is in the public domain.

    Is there any source of lens elements in the proper Crown and Flint glass? Even if an element is not the exact profile, it could be possible to get an optician to resurface it to the proper curvature, at lesst for the smaller sizes. It would cost some, but so do shootable, good looking antique lenses.
    Drew Bedo
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    There are only three types of mounting flanges; too big, too small and wrong thread!

  2. #2

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    Re: Lens element sources and specs?

    I don't know anything about this, but maybe Edmund Optics might have something?

    https://www.edmundoptics.com/c/wire-...aAsIlEALw_wcB#
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  3. #3
    Nodda Duma's Avatar
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    Re: Lens element sources and specs?

    It would be nice if it were that simple, but that’s not how lens design works. The errors which need to be corrected are on the order of wavelengths of light. That type of precision requires the optical properties of the original glasstypes to work with the rest of the lenses… glasstypes which are no longer available. The new versions of the original crowns and flints are close, but not close enough that only one lens can be replaced. At the very least, both crown and flints in a pair would need to be replaced or modified.

    Optical fabrication is labor intensive, even today. A one-off lens of say 2” diameter will cost approximately $1000-$2000.

    Most old lenses in poor condition suffer only surface damage or balsam separation. This is cheaper to repair than replace, if a place can be found to repair them. Refurbishing lenses requires an understanding of optical polishing techniques, but professional optical shops aren’t willing to take on that type of work. They can’t make the business case with the current enormous and growing global demand for new optics. All the optical shops are busy with new fabrication. Lead times are insanely long, and they won’t make them longer to repair old unknown optics.
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    Re: Lens element sources and specs?

    This is the voice of reason and insight!
    Unless we have a person of unlimited wealth (and limited common sense) within the LF community, there is no chance of new production of lens elements that match the originals.
    There was a project to remanufacture the Dallmeyer 3B some years ago, due to apparent shortages/spiraling prices of the original. No matching currently available suitable optical glass types were discovered, so a modified optical design was adopted to create a “knock off” 3B. With quite successful results I believe.
    The sandpits that Chance Bros. used for Dallmeyer (and almost all UK and some French) glass could be relocated and brought back into production - if anyone knows where they are located.
    The only other possibility is to collect scrap lenses from the same period, sort according to optical properties, melt and make suitable blocks. Or get oversized lens from a Projection lens of the right age and “whittle” them down to the correct surface curves and thickness.

    I really do think that supply/price of useable optics is not really a problem with current demand. The only common lens damage I see is from badly mounted rear pairs which have rattled and caused numerous edge flakes - ugly, but still very useable.

  5. #5
    Tin Can's Avatar
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    Re: Lens element sources and specs?

    Agree

    https://www.surplusshed.com/

    Inventory varies and changes

    Some grind their own telescopes, look into them

    However there seems to be a lot of good LF lenses still available

  6. #6
    Drew Bedo's Avatar
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    Re: Lens element sources and specs?

    Quote Originally Posted by Nodda Duma View Post
    Optical fabrication is labor intensive, even today. A one-off lens of say 2” diameter will cost approximately $1000-$2000.
    My round lensed prescription readers were much less than that and a large portion of thst was for the frames.

    The Lomo-Petzval lenses, though smaller, are well under a grand and that's for four elements with all the barrel parts too.

    There must be a way to get replacement glass parts for an antique Petzval formula lens. The curvature can be measured from the old elements, given the flint and crown glasses.

    For as much as an optically useful Petzval with nice brass costs today, in the thousands for some, I'd think there would be a niche market for replacement glass parts and whole, new-made lenses as well.

    Given the sucess of the micro four thirds scaled Petzval lenses, I expect that there are wet plate photographers out there that would pony up what it would cost for a replica Petzval with 8x10 coverage . . . even though its not an antique.

    The Petzval lens is 19th Century technology that was cutting edge in the 1840s. Today we have sophisticated CAD with CNC directed manufacturing that is scalable up and down. There is a "maker" culture evolving, just look around YouTube. The TravelWide project and the WillTravel cameras are an aspect of that.

    Creating a period equivalent Petzval lens today has got to be possible.
    Last edited by Drew Bedo; 8-Dec-2021 at 06:53.
    Drew Bedo
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    There are only three types of mounting flanges; too big, too small and wrong thread!

  7. #7
    Nodda Duma's Avatar
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    Re: Lens element sources and specs?

    Couple of things:

    The original glass properties are not some long-lost mystery like Damascus steel or made from some super special ingredient like Himalayan salt. Magic doesn’t exist in the era of modern (post-1800) era of science, only corporate proprietary info. As mentioned above, the prescription is well known.

    No, the issue is RHoS compliance: The old glasses were lead glasses and can therefore no longer be manufactured for regulatory / environmental reasons. We don’t like our glass melting experts getting lead poisoning in the industry, or creating lead-contaminated rain downrange of the glass factories.

    The glass manufacturers formulated lead-free equivalents decades ago, and to replicate the old prescriptions requires tweaking of lens shapes. From an optical design viewpoint these tweaks are inconsequential: The new 3B’s that Stephen mentions above *are* Petzvals from my perspective: They correct aberrations in the same way, at the same Fields of View, with the same resulting characteristics. In fact it’s probably *more* of a Petzval because modern manufacturing means they perform closer to the design.


    Drew, the difference between making your eyeglass lens and an imaging lens is analogous to the difference between using a pencil sharpener and the fine carpentry of a master woodworker. One is cheap and anybody can do it by sticking it in an automated machine, the other is expensive and takes time and hard-earned skill.

    To your last point: Undoubtedly so.. It’s something I’d like to do for folks, but the price point at realistic quantities is a tough nut to crack. You can get a feel by reviewing the pricing of Tri Tran’s beautiful signature lenses, which houses a single meniscus element. A new Petzval of similar build quality would be 1 1/2 - 3 times his pricing (just a guess, but a guess from knowing what optics cost).

    In any case, fun topic and I think there’s some room to play for this stuff. I probably sound like a negative nilly, but it’s really just pragmatism from dealing with optics design, costs, and schedules on a daily basis. The fun is in figuring out how to pull off a new lens for the community.
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    Re: Lens element sources and specs?

    There is wide range between meticulous and frivolous point of view in to the problem. One of the best sources for missing optical elements is this forum. Everybody has bits and ends, orphaned barrels, cells, etc. with no resale value. Just nobody rise an interest?

  9. #9

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    Re: Lens element sources and specs?

    I'd look on the various optical (EdmundsOptics, ThorLabs etc.) or surplus sites (too many to name) then find all, or most, of the required lens elements there. Barrels are also available from the optics suppliers, or machined from nylon(?), or 3D-printed if one isn't too fussy and the aperture can be waterstone-stop style holes. If one really wants an old formula lens, then it should be possible to assemble one after some research and without grinding elements yourself. Good luck!

    Edit: Here in Europe, for my workplace, I have used ThorLabs and Mitutoyo parts to build an automated microscope for one of our QA lines with total optical parts costs of around €2300. They (and other optical vendors) have various series of standard-ish fittings and sizings which permit assembly of a custom unit without machining -- but the mount is being made in our toolmaking shop and might end up being the most expensive part, as we have to 'pay' internally!
    Last edited by MartinP; 7-Dec-2021 at 15:28. Reason: Added example.

  10. #10
    Drew Bedo's Avatar
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    Re: Lens element sources and specs?

    Regarding the reference to Damascus steel: I take your point, and its a pretty good example.

    Damascus Steel" would have been a great on-point example thirty years ago or so. In recent years though, there has been serious research on what made the pre-modern era Damascus what it is. Craft oriented smiths have lately taken that research and groped their way towards creating similar to identical formulations in small crucible batches much as the ancient steel was made. Web searches using "Wootz" will turn up Wikipedia articles and YouTube videos of this process. I; liked the analogy of the pencil sharpener too.

    o there isn't even leaded crystal stemware anymore either? I imagine that the radioactive formulas are forbidden as well. Hope the environmental vigilantes never hear about the Thorium and Lanthanum doped glass on our priceless (or pricy) vintage lenses!


    I had no idea that re-creating an LF Petzval lens with modern materials and techniques on a craft basis would be so complex. My thanks for the excellent explanations. Too bad the Lomography folks have no interest in that. S
    Drew Bedo
    www.quietlightphoto.com
    http://www.artsyhome.com/author/drew-bedo




    There are only three types of mounting flanges; too big, too small and wrong thread!

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