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Thread: Large format camera optics

  1. #1

    Large format camera optics

    I would like to build camera with A4 sized negative (21cm x 30cm) or something near that size. Only proble I have is the lens.

    Negeative material will be cyanotype-paper, which means that pinhole is not an option. (Few months explosure is too long even for me)

    So I need a lens with following:

    1) Reasonable fast lens (One day explosuretime shoud be enough)
    2) Focusing (or if not possible then allways focused to infinity because I would not like to construct Bellows)
    3) Large FOV. I just love wide angle pictures

    Reasonable Vingetting or slight softnes are not problems. I do not need extreamly sharp images.

    What kind of lenses I could use with this camera? Is there a cheap way to get any lens just for my needs?

  2. #2

    Large format camera optics

    You could check out Greene's Primitive Photography to get lens ideas, but there might be a hitch. Cyanotype is one of the processes that need ultraviolet light for exposure, and most glass doesn't transmit UV very well. I think the reason that cyanotype prints are typically contact prints is that enlarging lenses don't transmit enough UV, even if you have a UV light source. It might be that even a fast lens won't pass enough UV for your needs.

    Greene also discusses using home made calotype negatives that will work with simple lenses.

    If you really want to use cyanotype, there are simple lens elements available that are made from either fused quartz or synthetic sapphire that do transmit UV. They are not cheap, however. Also be aware that UV will come to focus at a different distance from the lens than visible light, so if you focus using a visible light image, it won't be in focus for the UV the cyanotype responds to and you'll need to compensate.

  3. #3

    Large format camera optics

    Yes, I have not read an opinion yet that in-camera alt-process exposures are possible...to the contrary. I'll bet most of those responses are based on the same inherited knowledge...

    A number of the alt-processes will work with deep blue as well.

    Look up Mike Ware's processes. There might be one that has some promise for direct exposure...it' sone of the less common things...ziatype, something-rex, I can't remember.

    I thought I read someone contemplating the possibility of a recent revised chemistry being faster than others.

  4. #4

    Large format camera optics

    Ha! Have I fallen for another urban legend? Needless to say I haven't tried this, and my only experience with such things is in the not-very-closely-related field of fluorescence microscopy. Microscope users pay serious money for quartz optics when they need to get UV through them. Yet, that isn't the same thing as exposing a cyanotype.

    Well, at least my recommendation of Greene's book may be useful. I'll be very interested to see how this turns out.

  5. #5

    Large format camera optics

    Terry King's cyanotype rex process is supposed to be fast enough for in-camera exposures, but someone tried it at the Pittsburgh workshop with no success. Don't know the details, but it might be worth investigating.
    http://www.hands-on-pictures.com/html/rexhow.html

  6. #6

    Large format camera optics

    Sad... I think I have to bury this idea and buy some Welding glass to get several hour explosure. It is not the same, but it has to be enugh.

    I still think that cyanotype camera in cool idea.

  7. #7

    Large format camera optics

    Hey , dont bury the ideas , they are there for to find a cure.
    Why you are not trying pinhole ? I think it is transparent to uv

    Best ,

    Mustafa Umut Sarac

  8. #8

    Large format camera optics

    Yes, pinhole will work for uv....but if you consider how long the exposures are contact printing under a uv source, with a pinhole aperture size...I guess you might as well start doing some math to see how long an exposure...whether you can complete it yourself or need a child or grandchild to pick up the torch.

  9. #9

    Large format camera optics

    Quote Originally Posted by murrayatuptowngallery
    Yes, pinhole will work for uv....but if you consider how long the exposures are contact printing under a uv source, with a pinhole aperture size...I guess you might as well start doing some math to see how long an exposure...whether you can complete it yourself or need a child or grandchild to pick up the torch.
    I have already made some calculations and with extreme wide angle explosure times with large format would still be something like months with bright sunlight (no exoplosure at night is considered).

  10. #10

    Large format camera optics

    Well, think positively. It seems like it is not impossible.

    I wonder if the pre-flashing technique for paper negatives can be used for the iron-silver slow processes.....

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