Page 1 of 3 123 LastLast
Results 1 to 10 of 29

Thread: lens that can take advantage of hi resolution films like CMS20

  1. #1

    Join Date
    Jul 2008
    Location
    London
    Posts
    114

    lens that can take advantage of hi resolution films like CMS20

    hi

    I see that adox CMS20 can resolve 800 line pairs and is available in 4x5
    are there any lenses in any format that can get any where near this
    could microfilm cameras ?
    what lens did they use ?

    if not then
    what is the point of such a film

    robin

  2. #2
    Nodda Duma's Avatar
    Join Date
    Nov 2014
    Location
    Batesville, Arkansas
    Posts
    1,116

    lens that can take advantage of hi resolution films like CMS20

    Yes a diffraction-limited (or close to) visible optic faster than f/2.3 will resolve that spatial frequency.

    There are fast telescope optics out there which will do this (the Schmidt Camera comes to mind)
    Newly made large format dry plates available! Look:
    https://www.pictoriographica.com

  3. #3

    Join Date
    Jul 2008
    Location
    London
    Posts
    114

    Re: lens that can take advantage of hi resolution films like CMS20

    Thanks Nodda

    That's interesting
    I'm now looking at microfilm cameras that formally photographed newspapers into 16mm film
    Used in reverse it may well image jewellery onto 5x4 or even ULF

    Found one for £6 online ... So we will see

    Best

    Robin

  4. #4

    Join Date
    Feb 2008
    Posts
    41

    Re: lens that can take advantage of hi resolution films like CMS20

    I have a friend who used to manufacture digital scanbacks. He tried to commission a lens that could match 10,000 pixels per 2.67" (3750 ppi). He couldn't find a vendor to do the job. Expensive telescope optics aside, microfilm photography is done but the strangest folks. I had some working for me when I was a department head at a government agency. There is little high quality going on there.

    I doubt you can find a off-the-shelf lens to do the job.

    I'd be happy to be wrong. Please show me!!

    Tim Vitale
    Conservator
    Oakland, CA

  5. #5
    Nodda Duma's Avatar
    Join Date
    Nov 2014
    Location
    Batesville, Arkansas
    Posts
    1,116

    Re: lens that can take advantage of hi resolution films like CMS20

    Tim, I agree: Good luck finding an off-the-shelf lens. The only thing that comes to mind is a Schmidt camera setup.
    Newly made large format dry plates available! Look:
    https://www.pictoriographica.com

  6. #6

    Join Date
    Feb 2008
    Posts
    41

    Re: lens that can take advantage of hi resolution films like CMS20

    Right, my friend couldn't find large format lenses beyond 80 lp/mm, and 100 lp/mm seemed to be vaporware. I saw some of the tests and they just couldn't hold up.

    Is there some application that I don't know about using a telescope as a substitute for a large format lens on a view camera? Really, I don't know.

    Tim Vitale
    Conservator
    Oakland, CA

  7. #7
    Nodda Duma's Avatar
    Join Date
    Nov 2014
    Location
    Batesville, Arkansas
    Posts
    1,116

    Re: lens that can take advantage of hi resolution films like CMS20

    I was about to say I have no idea then I remembered that I have a Kodak Aero-Ektar sitting at home lol. This is rather academic, but the need for aerial/satellite reconnaissance in the film era would have seen very fast (faster than f/2.7) telescope-type objectives corrected over a large film plane. Could they realistically resolve 800 lp/mm? I'd have to measure the optical MTF of an example to know for sure. Mine won't..it's an f/6. But something along those lines...designed to look far away at high resolution...would be heading down the right path.

    Other than that, large observatory telescopes have really big image circles.
    Newly made large format dry plates available! Look:
    https://www.pictoriographica.com

  8. #8

    Join Date
    Jan 2002
    Location
    Besançon, France
    Posts
    1,616

    Re: lens that can take advantage of hi resolution films like CMS20

    Quote Originally Posted by brighamr View Post
    hi
    I see that adox CMS20 can resolve 800 line pairs and is available in 4x5
    are there any lenses in any format that can get any where near this
    could microfilm cameras ?
    what lens did they use ?
    Hello from France.

    I have personnally used in the past two kinds of highly specialized lenses capable of delivering well above 300 cy/mm on a pĥoto-chemical detector, silver halide plates or photoresist/chromium photomask plates.

    The first example was a lens made in France by Cerco, a 100 mm f/4 lens dedicated to fabricating photomasks from an enlarged drawing on paper. Years ~ 1982 - 1984, our lab had bough a used repro bench from an institution who stopped making photomasks by this technique, already obsolete at the time.
    The lens was a f/4 and was diffraction-limited, to be used in monochromatic green light (there was simply a green filter permanently mounted in front of the lens), and in a very limited range of magnifications like 1:20 or 1:10. Plates in use were 2-1/2" square, silver halide high-resolution glass plates with a resolution above 500 cy/mm.

    Among glass plates in use at the time there was the Kodak high-resolution plate type 1A, blue sensitive only hence probably unsuitable for use in green monochromatic light, and the legendary Kodak spectrocopic plate 649-F also used for holograms.
    I do not remember the manufacturer's specs for the lens resolution, but the absolute cut-off spatial frequency for a diffraction-limited f/4 lens is about 450 cy/mm for a wavelength of 550 nm (green).

    This 100 mm f/4 Cerco lens did not cover the 4x5" format, only 2-1/2" by 2-1/2", but I cannot see any reason why it could not have been designed in a focal length of 250 mm by scaling up the 100 mm design.
    Most probably, covering the 4x5" format, the resolution would have dropped down to about 200 or 300 cy/mm but by no way such a lens could resolve 800 cy/mm on a whole image field of 4x5".

    The second example, years 1989-2000, was a 10X photorepeater lens by Carl Zeiss. Fixed magnification 1:10, object size = 10x10 cm (5" square photomask plates and 4" image field). The output object was a photo-repeated mask, photoresist+ chromium on glass plates.
    I have no idea of the focal length and the f-number of this Zeiss lens, for sure the field angle was very narrow like in a telescope lens. It used mercury arc lines for illumination, the G-line at 435 nm and the H-line at 405 nm.
    The resolution limit, on a field of 1x1 cm, was 1.4 micron for the ultimate period (0.7 white bar plus 0.7 adjacent dark bar = period of 1.4) and the corresponding spatial frequency is 1000/1.4 = 700 cy/mm. Results obtained only when the machine was properly tuned, and this demanded quite an effort by doing time-consuming crossed-tests for best focus and best exposure time.
    The effective f-number N for a diffraction-limited lens capable of passing 700 cy/mm @400 nm is N = 1.4/0.4 = 3.5 ( a f/3.5 lens).

    But the requirements were: monochromatic blue or near-UV light ; fixed magnification, and the image field was 1cm square only.
    But it can certainly be used reversed with a 1cm object to make an enlarged image on a 4x5" sheet of film ... provided that you are able to properly focus the image
    But the resolution limit on the 10x image covering a 4x5" field would only be 70 cy/mm... any good film could be used in this application, no need for a 800 cy/mm microfilm.


    if not then
    what is the point of such a film
    robin
    This is a zero-grain film for those who hate the horrible granularity of Tri-X and HP5

  9. #9

    Join Date
    Feb 2008
    Posts
    41

    Re: lens that can take advantage of hi resolution films like CMS20

    I've heard of these (generic) fabled lenses. Thanks for all of that.

    Tim Vitale
    Conservator
    Oakland, CA

  10. #10
    Jac@stafford.net's Avatar
    Join Date
    Dec 2012
    Location
    Winona, Minnesota
    Posts
    5,413

    Re: lens that can take advantage of hi resolution films like CMS20

    Quote Originally Posted by Emmanuel BIGLER View Post
    [... snip great article ...]
    This 100 mm f/4 Cerco lens did not cover the 4x5" format, only 2-1/2" by 2-1/2", but I cannot see any reason why it could not have been designed in a focal length of 250 mm by scaling up the 100 mm design.
    Can a lens be scaled up, retaining the proportions to the same resolution? I really do not know, and having wrestled with the issues of down-scaling aircraft as a young man I usually question intuition. I disassembled a Pacific Optical 3" Biogon and found it had fewer elements than the 38mm. (I've no idea whatsoever of the PO's resolution. Never even tried to look it up.)

    Thanks for the great article!

Similar Threads

  1. How Lower Resolution Lens Works on Large High Resolution Wet Plate Negative
    By Mustafa Umut Sarac in forum Lenses & Lens Accessories
    Replies: 2
    Last Post: 16-Jan-2014, 15:04
  2. ADOX CMS20 5x4 sheet film
    By Adrian Roy in forum Darkroom: Film, Processing & Printing
    Replies: 13
    Last Post: 25-Oct-2010, 08:21
  3. Replies: 13
    Last Post: 9-Jul-2010, 02:19
  4. Any advantage to LF?
    By John Kasaian in forum Style & Technique
    Replies: 11
    Last Post: 4-Feb-2010, 22:56
  5. Real resolution of films?
    By Glenn Kroeger in forum Darkroom: Film, Processing & Printing
    Replies: 6
    Last Post: 26-Jan-2001, 18:19

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •