Process Lenses for Large format

Discussion in 'Large Format' started by peterkinchington, Mar 20, 2018.

  1. I have just purchased a 300mm f10 - lomo rf3 process lens for my 4x5 view camera. Does anybody have experience with this lens or any process lens for landscape applications?
     
  2. Process lenses are very sharp at 1:1, but fall off at longer distances. They often cover the format only at close focus, vignetting badly at infinity. You might be okay using an 8x10" lens on a 4x5" camera, but not one designed for 4x5". I have experience with a 6" Goetz Dagor to that effect.
     
  3. Thanks Dan for the comprehensive paper on your lenses. The lenses I currently have (and have yet to try on large format are a 90mm f8 super angulon (single coated I think) a 120mm f6.8 angulon (linhoff badged) that gave good results on 35mm kodachrome and now the 300mm f10 lomo RF3 - I got the RF3 so that I could get full movement with my standard bellows. I bought all the lenses because they were very affordable - I usually find that the lenses are not the limiting factor for my work. I tend to use very small apertures.
    And thankyou Ed - I believe that the RF3 can cover 8x10in with movements.
     
  4. Oh and thanks Dan for your article on Apo-Nikkor process lenses.
     
  5. Ed, you are mistaken about at least some process lenses' performance. Badly mistaken.

    You are right about some process lenses' coverage, wrong about others. Many are narrow angle lenses. The big exceptions are G-Clarons and Konica Hexanon GR IIs.

    Dialyte type process lenses such as, in alphabetical order, Goerz Apo Ronars, Nikon Apo-Nikkors (symmetrical type), Rodenstock Apo-Ronars and Schneider Repro-Clarons hold their corrections very well at all distances. So, surprisingly, do at least some apochromatic tessar types such as Nikon Apo-Nikkors (asymmetrical type) and TTH Apotals (some sold as Cooke or TTH Copying Lenses). So do heliar types such as Boyer Apo-Saphirs and Voigtlaender Apo-Skopars. Among six-element process lenses dagor type Schneider G-Clarons and plasmat type G-Clarons also do very well at all distances.

    Try them, you might like them. Especially dialyte type Apo-Nikkors.

    I can't find it now but I've seen Rodenstock propaganda that asserted that Apo-Ronars were superior at distance to all contemporary telephoto lenses.

    Among less known and harder to use types, Konica Hexanon GR IIs are outstanding. I once shot a 210/9 GR II against a 200/4 Apo-Nikkor AIS. At all apertures from f/9 down and at all distances that GR II was measurably sharper had contrastier.

    No all process lenses are good at distance. So-called wide angle process lenses, e.g., Process Nikkors and G-Claron WAs, that are 4/4 double Gauss types perform very poorly at distance.

    Try them, you won't like them.

    About Dagors' coverage. Echt f/6.8 and f/7.7 Dagors from Goerz are absolutely positively not 90 degree lenses. They're also not process lenses.
     
  6. Dan what do you think about apo-tessar design process lenses for landscape work?
     
  7. Dan I am sorry - I see you answered this question in your last post.
     
  8. As Dan says, most process/copy lenses are modified Tessar or dialyte types. As such they have a minimum coverage angle of 40 degrees or so, and are designed not to vignette - otherwise they'd be pretty useless for evenly-lit flat copy. Hence the maximum apertures of f/9 or f/10 with well rounded irises.

    Even assuming a hard cutoff at 40 degrees, a process lens of 210mm would easily cover 5"x4" at infinity. And IME be exceptionally sharp.

    Beware amber or yellowed Apo process lenses. The discoloured element(s) usually indicate the use of radioactive thorium glass. This increasingly becomes a gamma emitter with age. Something I wouldn't recommend having around.
     
  9. Is a significant amount of radiation emitted by thorium glass?
     
  10. Does thorium glass emit significant amounts of radiation?
     
  11. Peter, Joe, for an informed assessment of the hazards of using lenses that contain thoriated glass, see Aero-Ektar Lenses. The only process lenses I'm aware of that contain thoriated glass are TTH Apotals (also badged Copying Lens) and Repro-Clarons. Some say that late (but when?) Repro-Clarons don't contain thoriated glass. My TTH tessar type process lenses were yellowed on arrival, also my 55/8 Repro-Claron. Basking for several months under a dim UV-B bulb cleared all of them. My 210 Repro-Claron was clear on arrival.

    Joe, the majority of process lenses that come to the US market are plasmat or dialyte types. The UK market may be different. See the Apo-Nikkor article (link in post 2 above). For links to catalog and other information on the majority certainly not all) process lenses that regularly come to market see Where to look for information on LF (mainly) lenses.

    Peter, if you're interested in moving up to large format, to my taste the best anglophone LF forum is largeformatphotography.info/forum.
     
  12. Hi Dan,
    I will check out the forum you mentioned. Also I saw in your apo-nikkor article that you photograph fish. So I sent you some images I took on Sunday underwater at a beach near Melbourne, Australia to your hotmail address.
    Cheers Peter
     
  13. e-mail sent. You should post a link to your site. I think people would enjoy your work.

    Cheers,

    Dan
     
  14. "Does thorium glass emit significant amounts of radiation?"

    - Most certainly.
    An Aero Ektar and TTH Apotal both sent a radiation monitor singing at a few inches distance. Neither a sheet of steel nor a lead (Pb) brick attenuated the count significantly. Conclusion: gamma radiation at a level well above acceptable exposure levels for non-monitored personnel.
     
  15. OK after reading the article from Dan and your radiation readings Joe - I think I will stay clear of Thorium glass lenses.
    Cheers Peter (Kanga)
     
  16. You'll be ok with them as long as you don't keep them under your pillow or carry them in a pants pocket. Dr. Briggs was quite explicit about that.

    But Apotals and Repro-Clarons aren't the only process lenses. Stick with coated Apo-Artars, symmetrical Apo-Nikkors and Apo-Ronars. Don't forget Apo-Saphirs and, if the focal length suits, Konica Hexanon GR IIs.
     
  17. Dan thanks for the info.
    Cheers Kanga
     
  18. FWIW, Cox in his book "Photographic Optics" classes dialyte type lenses as triplets. He reasons that the two inner negative elements can be seen as a single split element.

    Whether or not any further optical corrections can be got from varying the inner curvatures or air spacing would disprove or reinforce his assertion. I'd have to find time to play with an optical simulator to find out.
     

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