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  1. Re: Show your 3D printed LF photography related thing

    I have an SLA printer, so smokey black resin
  2. Re: Show your 3D printed LF photography related thing

    I converted a scan of a dry plate into an STL file and printed it out. The thickness was a function of grayscale. Here is the result.

    223546

    223547
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    Re: New articles by Jeff Conrad on DoF

    Thanks for bumping this thread up. There's some new optics guys at work since 2018 that I will forward this article to.
  4. Re: Question about Lenses and focal lengths... in German

    Pardon if I nerd out on the topic a bit.

    Dan, the 0.5 (in air) limit for f/#can be misleading, as the 1/2NA = f/# is a small angle approximation so it doesn’t truly indicate what the lens is...
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    Re: Lens element sources and specs?

    Haha. I’ve been known to tell Program managers “we can do anything you want, as long as you throw enough money at it.” The look I get back hasn’t changed in 20 years. :D
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    Re: Lens element sources and specs?

    Lanthanum glass is used quite often.. the radioactivity is so low that it is below natural background levels and thus not considered hazardous. I’d be willing to bet there is a lanthanum glasstype...
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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...
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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...
  9. Re: The Problem with Modern Lenses.. transfered to those new to view camera image mak

    I suppose it depends on your definition: Marketing terminology or what designers identify as reliance on image processing to relieve the burden on the optics. I can tell you as an active,...
  10. Re: The Problem with Modern Lenses.. transfered to those new to view camera image mak

    Oh..very good question. Smart phone optics are an example of this, where image processing is used to enhance the image quality for display on a smart phone screen. This makes up in large part for...
  11. Re: The Problem with Modern Lenses.. transfered to those new to view camera image mak

    Optics aren’t designed by a computer. The drudgery of ray trace calculations is performed on a computer, but there is definitely a person designing those optics.

    The difference between optics...
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    Re: Turner-Reich modifications?

    ridax,

    I’ve gotten pretty good at repairing balsam separation in the Turner Reichs, and can confidentially say your first approach won’t work. In fact, it will cause the lens to adhere to the...
  13. Re: Gundlach Anastigmat 12" convertible hood size?

    They aren’t on the Anastigmat. Lens installs from the rear. The threads on that lens are primarily for control of stray light.


    Brian’s suggestion is your best bet, Paul
  14. Re: Regarding depth-of field curvature with tilt

    This all sound correct and good for how depth of focus / depth of field works. The analogous equations in the world of optical design typically get derived into determination of hyperfocal distance,...
  15. Re: A Heliar with an adjustable front group?

    In my humble opinion that seems like a hack job by a previous owner.
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    Re: Stearman Press SP-810

    Yes, that’s exactly what I do. Start at a slightly higher temp so that the average temp throughout development is exactly what it should be. It works well… I have a few examples in my media feed...
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    Re: Stearman Press SP-810

    Hey Kiwi,

    I’ve developed E-6 8x10 in it — Aerochrome too — and for E6 in general you have to be aggressive in your agitation. For the SP-810 I pick it up and slosh it around as much as I dare. ...
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    Re: Podcast with Sandy King

    It was a good podcast. Those guys are great.. the UK is turning into a nice little hotbed of “new” large format photography.
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    Re: Stearman Press SP-810

    Definitely contact Tim at Stearman Press. He will want to know about any potential deformation of the lids preventing it from doing what it’s supposed to, and is the person best positioned to help...
  20. Re: Orotone work in Dallas on 32” x 38” dry plates

    The glass was 6mm thick or ~1/4”. Basic soda lime float glass, untempered. Each sheet weighed about 30lbs.
  21. Orotone work in Dallas on 32” x 38” dry plates

    Recently I coated very large 32” x 38” dry plates for D Anson Brody, who is using them for an Orotone restoration / replacement project in Dallas, Texas. This has received some publicity down there....
  22. Re: Anyone hear from Famous Format (New 55) ?

    Have not heard a word about the two bottles of monobath that I ordered in early December.

    FF is a ghost ship: https://www.famousformat.net/about
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    Re: Chamonix Camera Rental Services

    Dangit Hugo, lol. I want to try out ULF but I don’t want to *more easily* try out ULF. ;-; :)

    Awesome idea.
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    Re: Negative Supply LM1 incident meter

    Easier to design into a new meter, of course. Ideally it goes right over the sensor or replaces the UV/IR cut filter which the meter undoubtedly uses. Also need filter factor compensation and...
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    Re: Negative Supply LM1 incident meter

    I asked Negative Supply a question on their live stream today about accommodating a spectral filter to provide accurate metering for wet / dry plate — something no meter on the market can do — and...
  26. Re: Spectral sensitivity of collodion and orthochromatic film

    As Denise explains, orthochromatic sensitivity goes through green, yellow, into orange. It has a measurable response at least to 610nm, depending on the specific sensitizing dye.

    Unsensitized...
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    Interview About Making Dry Plates

    A week or so ago, Graham of Homemade Camera Podcast had me on his show to talk dry plate making.

    http://homemadecamera.com/e70-jason-lane-and-chromatic-abberation/
  28. Re: Extremely Dumb Questions about Lens Systems (Specially Cooke triplet)

    It is correct: a super non-technical variant of the most generic “inverse of optical power” definition for the benefit of the OP while tying it in to his other q’s. “It is a design value” is key. ...
  29. Re: Extremely Dumb Questions about Lens Systems (Specially Cooke triplet)

    1) focal length is how far from the film the lens has to be held to produce an image that’s in focus. It is a design value, and indicates how wide a view the lens projects onto the film.
    2) field...
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    Re: New starter from Australia

    Welcome aboard! From someone who is also a veteran of sleepless astrophotography nights.
  31. Re: A DIY 123mm f/8 Cooke split triplet for 4x5

    I’m going to use that in a meeting in the near future
  32. Re: A DIY 177mm f/8 Cooke triplet for 4x5 from off-the shelf lenses that YOU can bui

    You can get it to work, but it won’t be a rapid rectilinear as off the shelf achromat are the wrong lens shape to correct spherical. You will be able to correct distortion, lateral color and, with...
  33. Re: Making Lenses With Shorter Focal Length from Cheaper Materials

    I think my advice was good luck. I have not seen 3D printed lenses implemented in the professional optical design world. I have seen attempts — funded research and simple prototypes — but attempts...
  34. Re: A DIY 123mm f/8 Cooke split triplet for 4x5

    Dan that made me chuckle. For future reference, GOTS = government off the shelf GFE = government funded equipment.

    Thorlabs has a very few…all the wrong shape for minimizing spherical...
  35. Re: A DIY 123mm f/8 Cooke split triplet for 4x5

    Dan I looked at COTS lens designs which would need meniscus lenses. Meniscus COTS lenses are rare and the right set that would be needed don’t exist unless something has changed in the past 2-3...
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    Re: Pencil of Rays

    Just to be clear I’m not a mathematician :) , I’m a lens designer. I design optics that are built (the initial prototypes by me) and used in imaging and laser systems and which do what they’re...
  37. Re: A DIY 123mm f/8 Cooke split triplet for 4x5

    Nice work. The 0.1mm airgap between the two front lenses is tight. Can you reverse the order of those two front positives and pull them apart slightly?
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    Re: Pencil of Rays

    A good site. Very basic, but he knows optics and more importantly looks like he has a “feel” for how they work.
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    Re: 6 1/2 x 8 1/2 cameras?

    No problem and good luck! Whole plate format is a great format. The aspect ratio is really nice.
  40. Re: Which would be easier to build - 8x10 SLR or TLR?

    Fine fine. :) But a roof prism for it would be glorious
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