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Thread: Lens element sources and specs?

  1. #21

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    Re: Lens element sources and specs?

    Quote Originally Posted by eggplant View Post
    I'm slowly learning to input patent data of lenses into programs like OSLO.EDU, so performance can be quickly estimated. Unfortunately, alot of the cheap third party ones are impossible to find patents for (nor are patents reflecting the produced item).
    See dioptrique.info, which has > 1000 prescriptions, many taken from patent data.

  2. #22
    Nodda Duma's Avatar
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    Re: Lens element sources and specs?

    Quote Originally Posted by Dan Fromm View Post
    See dioptrique.info, which has > 1000 prescriptions, many taken from patent data.
    I have an ongoing project to update the dioptrique prescriptions to zemax format. I’ve done most of the 1800s so far. There were a few minor corrections needed here and there.
    Newly made large format dry plates available! Look:
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  3. #23

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    Re: Lens element sources and specs?

    I haven't followed this from the beginning or read all the related threads. But when you have formulas that describe a design, you can use them in several ways.

    Mostly this seems to be interpreted that you have specifications telling you what you want to achieve and then the formulas let you calculate what lenses you need to achieve your specs.

    But you can also use them to make a lens from lens elements you have around. This may mean you have to rework the formulas and/or put a computer to work to iterate through them to find the result. Reminds me of what we did with "minuit" in university: you have formulas with variables, a range for that variables, measurements and an "error function". Then let the computer find you the variables that fit your measurements.

    So I see no reason why you should not be able to make a certain lens from standard elements. If the elements you have fit the general need. It won't be possible if the formula specifies plano-convex lens elements and you have only double convex around.
    Expert in non-working solutions.

  4. #24

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    Re: Lens element sources and specs?

    Quote Originally Posted by Dan Fromm View Post
    See dioptrique.info, which has > 1000 prescriptions, many taken from patent data.
    I've had this bookmarked, great resource to model around, I couldn't find any downloadable files to use, though.

    https://www.lens-designs.com/ contains a great deal in both Zemax and OSLO format, with good detail on what lenses the patents are. Older stuff naturally suffers from not being as well annotated though.

    These websites will be good for seeing what I'm trying to recreate - but won't contain the data of the lenses I'll be using, which are third-party, vintage 1970s-1990s zooms.

    Quote Originally Posted by Nodda Duma View Post
    I have an ongoing project to update the dioptrique prescriptions to zemax format. I’ve done most of the 1800s so far. There were a few minor corrections needed here and there.
    Would you be able to check compatability with Winlens3D? Or make them in that file format?

    This is the only program which people will be using, because it's free and doesn't have a surface limit. Zemax and OSLO are impossible to access.

    Winlens3D is able to import designs from both, so you wouldn't have to do everything from scratch- the issue is that some refuse to be loaded due to fatal errors, and some other quirks. Using stuff from lens-designs.com here.

  5. #25
    Nodda Duma's Avatar
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    Re: Lens element sources and specs?

    I use Zemax, as does most of the lens design world, so into Zemax format they will go.

    The prescriptions are, however, universally able to be manually typed into any design tool.

    -Jason
    Newly made large format dry plates available! Look:
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  6. #26

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    Re: Lens element sources and specs?

    This is fascinating. I would really like to build a lens, maybe from surplus elements.

    Is there a good book or web resource for learning how to do this? Ideally, more than just recipes but not trying to get a degree in optical engineering.

  7. #27

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    Re: Lens element sources and specs?

    In previous DIY threads people have expressed the desire to rebuild historical designs. The reality is that one can't faithfully reproduce an existing lens design from off the shelf elements. Unless you're an optical designer and can re-compute the design, as in Nodda Duma's thread: https://www.largeformatphotography.info/forum/showthread.php?120024-A-DIY-177mm-f-8-Cooke-triplet-for-4x5-from-off-the-shelf-lenses-that-YOU-can-build

    That said, people do use single element lenses, especially for soft focus, so anyone can experiment. If you want to try a single element meniscus lens, get a positive meniscus in crown glass from any of the optical supply houses as mentioned earlier. (Crown glass is the default for single elements from eg Edmunds or other suppliers.) Use it with the concave side toward the subject, and aperture in front of the lens.

    If you want to approximate a more complex design with negative lenses, such as making a roughly achromatic lens, or a triplet, you'll need a negative element in flint glass. Flint glasses and crown glasses have different dispersions, which allows roughly canceling-out the chromatic aberration on-axis. Now the problem is that all of the inexpensive single elements from Edmunds, Thor, etc are crown glass. You can spend a little more for a flint glass concave element, or buy some of the achromat components from Surplus Shed - an achromat is made of a positive crown and negative flint. Using off the shelf lenses, you should be able to put together something that makes an image, but with significant aberrations (spherical aberration, off axis aberrations such as astigmatism and curvature of field). However, the results may be interesting.

    Books and resources on lens design tend to be technical by nature. A good one is Warren Smith's "Modern Optical Engineering." Willmann-Bell published a few lens/optics design books. They recently closed suddenly but it turns out the American Astronomical Society is taking over their business, so the books will become available again eventually.

  8. #28

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    Re: Lens element sources and specs?

    For those of you wanting to get into DIY optics, a contemporary photographer you may want to check out is Susan Burnstine. I've been reading this thread as it's progressed, but hadn't remembered her work until now. Her work is medium format, not large format, but she builds her cameras entirely herself. They are essentially cardboard boxes covered with tape, and a cast plastic single element lens. Cast plastic lenses are no where near as technically accurate as glass ones, but with them she is able to create amazing images nonetheless. She's hasn't done any workshops on how she makes the cameras, but it seems straightforward enough, especially compared to making glass lenses.

    anyway, I just thought some of you fellow DIYers may find her work interesting, she is probably my favorite contemporary photographer based on her work alone, though the DIY camera thing is awesome too. (image of one of the cameras bellow)
    Click image for larger version. 

Name:	Susan Burnstine Camera.jpg 
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    You can see her photographs on her website here: http://www.susanburnstine.com/

  9. #29

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    Re: Lens element sources and specs?

    Quote Originally Posted by reddesert View Post
    In previous DIY threads people have expressed the desire to rebuild historical designs. The reality is that one can't faithfully reproduce an existing lens design from off the shelf elements. Unless you're an optical designer and can re-compute the design,
    Well yeah- that is the task ahead of anyone here- if you want to get anywhere, understand why things act the way they do, the reason for the results you're getting, etc- some methods of lens designs will have to be employed.


    Quote Originally Posted by reddesert View Post
    If you want to approximate a more complex design with negative lenses, such as making a roughly achromatic lens, or a triplet, you'll need a negative element in flint glass. Flint glasses and crown glasses have different dispersions, which allows roughly canceling-out the chromatic aberration on-axis. Now the problem is that all of the inexpensive single elements from Edmunds, Thor, etc are crown glass.
    This is all abit excessive- maybe you missed my earlier post where I showed easy sources of diverse array of achromats, of different shapes and sizes etc from vintage zooms?

    Even if this didn't exist, achromatic close up diopters would be the way to go, or anything off the shelf- there is no need to compute one of the oldest corrected lens designs in history...

  10. #30

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    Re: Lens element sources and specs?

    For me, the most interesting part would be to do some simple design work and learn basic optical engineering (I'm an engineer by training -- always fun to do someone else's real job for a while).

    I like the idea of disassembling undesirable lenses and harvesting lens elements. I imagine you would get a variety of crown, flint and other types of glass in different types of lenses, especially if you chose lenses with lots of air gaps over cemented units. How does one go about characterizing what you harvest?

    If I could pick out a flint glass element, could I then design an achromat or other simple combination to have a desired focal length using Zemax or other software?

    And then buy the missing crown element(s) for my design from surplus websites or suppliers like Edmunds?

    There are lots of cheap used copies of Modern Optical Engineering online. I'll grab a copy.

    Is Zemax available to the hobbiest? The standard license is $3200/year. Are there other options?

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