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  1. #11
    MattKing's Avatar
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    With respect to standardizing exposure, this is a great opportunity to make use of an enlarging meter. I use an Ilford EM10 just for this purpose.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  2. #12
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    My set way of doing contacts is the same for every size of negative. I use the 50mm enlarging lens and put it at the right height so a 35mm carrier (the edges) will be in focus and a little larger than 8x10. I have the spot marked on the enlarger support. The negs are in PrintFile sheets and held down by a piece of glass from a frame (thin and not UV protective). I use the #2 filter and f8 for 8 seconds. This works for me and my enlarger (Beseler 23CIII), but I can't guarantee it'll work for others. Since I ALWAYS do them this way, I can spot under and over exposed frames easily.

  3. #13

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    I do the same thing as winger, except without a carrier in place and with the lens defocused. I've never noticed uneven lighting being an issue. It is more important to me to have all proof sheets receive identical exposure so that I can compare film development results and identify issues with the paper developer (i.e., degrading). I set the aperture so that the printing time for a good negative is about 15 seconds with a #2 filter.

  4. #14
    ic-racer's Avatar
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    Quote Originally Posted by MSchuler View Post
    with the lens defocused. I've never noticed uneven lighting being an issue. It is more important to me to have all proof sheets receive identical exposure
    Defocusing changes the effective aperture. Focusing on the edge of the negative frame is a super-easy way to ensure the same aperture between prints.

  5. #15

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    not sure why which lens you use matters -- light is light, the paper doesn't know where it's coming from, use a lens that lets you set the enlarger head at a convenient height. When I use my Focomat to make contact prints I leave the 50 on and set the height so it covers the contact printer.

    Then do a coupla test exposures to get proper time and away you go. Using an enlarger DOES let you use multi-grade paper and filters if you want.

    Same thing with the "enlarging paper" question -- the paper doesn't know where it is, all it knows is that it is exposed to light, so use whatever paper you have.

    If your light is uneven across the space, you need to look at your bulb's placement in the enlarger head so that exposure is even when you are making enlargements too.

  6. #16

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    Quote Originally Posted by ic-racer View Post
    Defocusing changes the effective aperture. .
    could that be explained in more detail please?

  7. #17
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    Quote Originally Posted by pdeeh View Post
    could that be explained in more detail please?
    The farther the iris is from the paper, the smaller the effective aperture.

    It is the same mathematics for 'bellows factor.' Just imagine the subject as the negative and the paper as the film. If the bellows were around the lens and paper, you'd have a view camera. All the equations for view cameras apply to enlargers.

    If you want a simpler explanation, try this: as you move the enlarger lens closer to the negative (farther from the paper) you will see the size of the projected image gets larger. If you have an enlarger meter you will also see that the image gets dimmer, which has to happen to conserve matter and energy.
    Last edited by ic-racer; 04-24-2014 at 12:44 PM. Click to view previous post history.

  8. #18
    ic-racer's Avatar
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    Quote Originally Posted by summicron1 View Post
    not sure why which lens you use matters --
    Check out the light falloff from this 40mm Componon HM. If you were to use that lens at f2.8 to make contract prints, the frames on your contact sheet at the corners only get about 40% of the overall exposure.
    https://www.schneideroptics.com/pdfs...on_28_40_1.pdf

  9. #19

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    Quote Originally Posted by ic-racer View Post
    The farther the iris is from the paper, the smaller the effective aperture.

    It is the same mathematics for 'bellows factor.' Just imagine the subject as the negative and the paper as the film. If the bellows were around the lens and paper, you'd have a view camera. All the equations for view cameras apply to enlargers.
    Ah yes, I see. Inverse square law? It doesn't change the aperture, but lowers the intensity of the light at the paper surface; However you can also defocus "the other way" (bringing the iris nearer to the paper surface), and so "opening" the aperture?

    Presumably though, if you always close the bellows up the same amount as well as maintain the same head height and lens aperture, you will always have the same light intensity at the paper surface anyway (all other things being equal)

  10. #20
    ic-racer's Avatar
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    Quote Originally Posted by pdeeh View Post
    Ah yes, I see. Inverse square law? It doesn't change the aperture, but lowers the intensity of the light at the paper surface; However you can also defocus "the other way" (bringing the iris nearer to the paper surface), and so "opening" the aperture?

    Presumably though, if you always close the bellows up the same amount as well as maintain the same head height and lens aperture, you will always have the same light intensity at the paper surface anyway (all other things being equal)
    If I were to use enlarger light to make 'standard' contacts, I'd experiment with various lenses, apertures, condenser settings and lens distances to find an optimum by printing the light source onto a piece of paper. Then record everything, including measuring the bellows extension. It is a lot of work; a bulb from across the room is almost always going to be more even. This is how poorly my 8x10 enlarger performed when I first got it:
    Click image for larger version. 

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