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  1. #81
    ic-racer's Avatar
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    Quote Originally Posted by Alex Hawley View Post
    Actually, this would best be done using a matrix of strain gages mounted in all three planes (x, y, z) at each corner of the frame, in the middle of each frame member, then a matrix at several points on the back and on the glass sheet. That would allow actual deflections to be be measured. The forces applied and bending moments could be calculated from those direct measurements. Of course that depends on the properties of the frame's materials, so then we get into the type of woods being used, wood grain orientations, saw orientation, and of course, moisture content at time of testing.

    Once the first test is complete, then we can vary the types of woods and joint constructions used in the frame, along with glass types and thicknesses. I'm excited!
    Actually, I saw some pretty well thought-out contact printers in use for aerial photography. I am enticed by the possibility of having the negative DOWN and the paper UP, so I can just open the lid and stick the proof strips down and pick them up again, without having to dissasemble a frame.

  2. #82
    ic-racer's Avatar
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    Quote Originally Posted by richard ide View Post
    . Not the best but it works....
    I have "paper clips and cardboard" also, but this is the point: if it's "not the best" then it doesn't work for me.

  3. #83
    ic-racer's Avatar
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    Quote Originally Posted by DeardorffV8 View Post
    In working with contact printing LF negatives I found I got sharper results with 8x10 and larger film sizes by using a vacuum frame. 5x7 and 4x5 were fine with a normal spring back glass contact printing frame.
    Thank you (and I'm not being sarcastic), this is exactly the kind of thing what to know.

  4. #84
    ic-racer's Avatar
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    Quote Originally Posted by CBG View Post
    I would urge the OP take a class somewhere and see the process done.

    Some things really are simple at their essence,

    C
    Actually would like to do that, there is a alt process workshop in my local area but this season's schedule is over.

  5. #85
    CBG
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    Quote Originally Posted by ic-racer View Post
    Actually would like to do that, there is a alt process workshop in my local area but this season's schedule is over.
    Thanks - but - I would beg you to stay away from alt processes till you are rock solid with basic silver based contact printing - too many new variables - my suggestion is that you do not need to add more to think about.

    Keep it simple. All this complexity: collimated light, twenty sheets of glass, ad infinitum is an albatross that will keep you from getting what you want.

    Thirty years ago, I used the exact opposite of collimated light. I contacted with a sheet of flashed opal glass and a pad of foam rubber. Long time ago, but it worked like a charm. The light coming out the back of flashed opal glass is what I imagine the inside of a ping pong ball would be. As diffuse as possible.

    C

  6. #86
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    Quote Originally Posted by CBG View Post
    Thirty years ago, I used the exact opposite of collimated light. I contacted with a sheet of flashed opal glass and a pad of foam rubber.
    C
    Why did you change?

  7. #87
    DBP
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    For over 30 years I have made contact prints the way my father, and his father before him, made them. 1. Place a piece of paper, emulsion side up, on a flat surface. 2. Place negative on paper, emulsion side down. 3. Cover with a clean sheet of glass (these days I wipe it with a microfiber cloth to clear off dust - TP was the old solution). 4. Expose to a light source (this ranges from my enlarger - racked all the way up so I lessen the chance of banging my head against it - to an old Kodak contact printing box - which admittedly reverses the order of the stack so paper is on top). If the curl of the negative or the paper is an issue I hold the glass down with my fingertips.

    If this worked in my grandparent's attic, my uncle's attic, my parent's bathroom, my pre-renovation basement, and my current combination basement and laundry room (and yes, I do have to deal with dust issues), then it should work anywhere.

  8. #88
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    Quote Originally Posted by DeardorffV8 View Post
    In working with contact printing LF negatives I found I got sharper results with 8x10 and larger film sizes by using a vacuum frame. 5x7 and 4x5 were fine with a normal spring back glass contact printing frame.
    ice-racer - If one feels better using a vacuum frame for 8x10 negs, fine, but something equivalent to a B&S mid-size 12x15 exposure-area split back contact frame is all you need. Pressure distribution against the thick, stiff back is even throughout and the interior glass and backing felt are always protected from external crap by the framed structure. Glass cleanliness and dust are a non-issue ... with a little logic.

    You do need the extra room of an oversized frame, be it for ease of handling just 8x10 silver paper, or for employing the necessarily-oversized 11/11.5 x 14/14.5 alt-process papers – an area you're guaranteed to enter once you see those beautiful contacts ... once you throw out the math you learned past sixth grade.

    PS - My math is PRE-sixth-grade! I have trouble keeping count of the drops coming out of an eyedropper much less determining the matrixical forces extant within a compounded medial plane that ecliptically reciprocates the inverted mass of american black cherry and 3/8" thick hyperventilated non-ultraviolet glass – an issue that dearly needs clarification by someone way smarter than me. Meantime, amazingly, I find my 8x10 plat prints perfectly sharp.
    Last edited by bruce terry; 10-30-2007 at 02:35 PM. Click to view previous post history.

  9. #89
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    I have a vacuum frame, but I feel that 8x10 can be happily printed with a good quality springback frame. The quality of a frame is important. I haven't seen an advantage to the vacuum frame until 11x14, and it's sloooow.

  10. #90
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    Quote Originally Posted by DBP View Post
    For over 30 years I have made contact prints the way my father, and his father before him, made them. 1. Place a piece of paper, emulsion side up, on a flat surface. ... snipped ...

    If this worked in my grandparent's attic, my uncle's attic, my parent's bathroom, my pre-renovation basement, and my current combination basement and laundry room (and yes, I do have to deal with dust issues), then it should work anywhere.

    Yup ... me too ... exactly .... works perfectly ... no math req'd.

    cheers eh?

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