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Thread: New 10x8

  1. #1
    500+ Posts DaCh's Avatar
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    New 10x8

    Here is my latest 10x8 camera. Commissioned by a local photographer.
    A usual rainy day as you can see by the rain drops on top of it.

    L1070151a.jpg

    Like my last 10x8 this has a curved film plane and can be used as a contact printer as well as a camera.
    The 58mm rotating filter mount has two pinholes, 0.6mm for taking and 3mm for printing.
    The mount is locked by the sprung catch below it.
    Slot in filter mounts in front of the pinholes allow coloured filters and a diffuser for the printing.
    Door at the end for loading the film.
    150mm focal length gives an effective aperture of f256 or taking and f45 for printing.
    The size of the printing aperture is decided to give the right sort of exposure times; it has no relevance to print quality.
    If you are thinking of making a large camera, this curved shape makes it a much smaller box that is really carry around friendly, well worth the effort.
    This camera is made from 6mm MDF top and bottom and two wraps of 0.8mm ply for the body. Black paint inside and out makes the thin ply light tight.
    Does light still exist if we're not looking?

    http://www.flickr.com/photos/dach_art/

  2. #2
    Nice design, David.

    I have a question about in-camera contact printing. Can you share your methodology and some examples? I wonder how off-axis light falloff affects the print; if the negative were exposed in the same camera, does the off-axis falloff cancel out between the negative exposure and the contact print exposure? That is, light falloff would make the corners of the paper negative more paper-white; which corners would then pass proportionally more light to the print during the contact printing phase; although during contact printing in-camera the light intensity in the corners is less; thus the compensating effect I'm guessing happens.

    Also, if you're using a large hole with diffuser filter for contact printing, how do you measure the light and figure your exposure? Do you aim the camera directly at the sun?

    Obviously, I haven't done this myself, hence the questions. I can see it being a valuable feature if the process can be repeatedly duplicated with good accuracy under variable lighting conditions.

    ~Joe
    "There was just that moment and now there's this moment and in between there is nothing. Photography, in a way, is the negation of chronology."-Geoff Dyer, "The Ongoing Moment"
    My Writing Blog: Joe Van Cleave's Blog
    My Pinhole Blog: Obscure Camera
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  3. #3
    500+ Posts colray's Avatar
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    The contact printing also has me puzzled . Can't see how the negative and paper could be held in good contact on a curved surface. But then thinking about it.. maybe the answer is in surface tension caused by the curved surface. Colin

  4. #4
    500+ Posts DaCh's Avatar
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    Hi Guys
    This whole thing started because of a project I have going on. I wanted to be able to produce a finished print right there where I captured the image without even leaving the place. Direct positive will not do it for several reasons. I decided that 10x8 was the smallest size, which would give a contact print big enough to display.
    It took a while to arrive at the camera but it eventually became a eureka moment and it suddenly all seemed rather obvious.
    Answers to your questions.
    1. How to make a contact print without a sheet of glass? Hold two sheets of paper together and see what happens when you bend them slightly. They naturally stick to each other.
    2. It worked so well I tried printing flat but without the glass, it does not work; much of the print is fuzzy because the two sheets are not in contact. I have never seen any fuzzy bits on my curved contact prints.
    3. Light fall off toward the corners. The curved film plane helps reduce light fall off, none is visible on my negatives. I calculate that it is no more than half a stop less in the corners than the centre. Any fall off will cause the corners to be lighter on the negative this will print darker on the print but the same lower light in the corners will reduce the exposure and reduce the darkening, so yes it should cancel itself out (more or less).
    4. Making the printing exposure. I use a translucent filter over the pinhole. The camera must not be pointed at the sun because the sun is a small bright point in the whole area of sky that the camera is gathering light from and a simple filter can not even that out. I get my exposure by pointing my incidence meter at the sky and double the exposure to allow for the light going through the paper and double it again to allow for the diffuser. The camera needs to be pointed at a large area of clear sky and this can be difficult especially around mid day when the sun is overhead so I hold the camera and turn it round during the exposure if I am worried about un-even lighting, seems to work very well.
    5. I have modified a single hole hole punch so it punches a half hole notch in the edge of the paper like we get on film, now I know which round the paper is when I am out and reloading in a changing bag.
    6. When I am out I process in a Paterson 5 reel tank just by rolling the paper round inside the tank and using 1 ltr of chemicals, then keep moving the tank around for two or three minutes to ensure the paper is fully developed.
    7. And I guess the last thing is…….yes I can (and do) reliable repeat my results. I think the hardest bit is just using paper negatives and deciding exactly where I want to place the tonal range and also considering the colours and how that will affect my exposure.
    Today I handed this camera over to its new owner so I will carry on using my Mk3 which is much more ugly but based on the same principle and dimensions. I posted a pic of it here a while back.
    http://www.f295.org/main/showthread....highlight=10x8
    I will let you know how the project gets on during the summer.
    Does light still exist if we're not looking?

    http://www.flickr.com/photos/dach_art/

  5. #5
    500+ Posts Ned.Lewis's Avatar
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    I remember the sheets in contact from the slight curve in a post of yours some time ago. It's very clever! I remember the phrase "so simple it hurts!" from that thread. This morning I was thinking about this and about Joe's question about falloff. There's a neat symmetry there, and something appealing about using a "pinhole" ( or close enough ) and daylight to make the contact print. I think if all the processes were linear ( rate of darkening of the negative, light transmission through the paper as the angle changes, etc. ) then it would perfectly cancel the light falloff... with the same sized pinhole to get the same amount of 'squint'. But we know the processes aren't linear ( s-curves, layers of resin, etc.. ) so my guess is that it compensates the falloff in a unique way... adding to the charm of course! I think it's great!
    Some photos: Ipernity
    ( pinholes and solargraphs mixed in among the rest)

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