? re: interpositives

Discussion in 'Contact Printing' started by jmal, Jul 22, 2008.

  1. jmal

    jmal Member

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    I want to enlarge my 35mm and 120 negs onto an ortho lith film for contact printing and was looking for any advice on the process. Not too long ago I read about using RC paper for the interpositive and then contact printing onto the film. Does this produce a sharp neg? Keep in mind that one of the more appealing points of some alt processes is that they are not as detailed and literal as silver prints. So, some loss of sharpness/detail is not a problem. Or, is it better to create the interpositive from ortho lith film as well? Any thoughts or suggestion are appreciated. Thanks.

    Jmal
     
  2. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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  3. jmal

    jmal Member

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    Thanks David
     
  4. Deckled Edge

    Deckled Edge Member

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    Contact prints of what size? I recommend you enlarge the 35mm onto interpositives of your final size (unless you are blessed with an 8x10 enlarger).
    For those processes that are "not as detailed and literal" that you find appealing, I would let the process dictate that, not a degraded interpositive. Most alternative process prints are contact prints from an original negative produced by a lens that gives the unique properties to the image. You may be disappointed when a limited negative area is enlarged and then subjected to processes that further alter the original. OTOH, this may be just what you are trying to accomplish. In any event, I have had good luck enlarging onto Efke PL 25 and contact printing the interpositive onto PL 25 and PL 100. Start small and use David's references. It's actually easier than you may think.
     
  5. jmal

    jmal Member

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    DE,

    I was planning on 8x10 contact prints--nothing larger. And, as you mention, whichever material I use, the interpositive will be the same size as the final print/negative. So, the queston remains: does an RC paper interpositive produce a usable final negative, as mentioned by Andrew Sanderson in BW Photography (UK)? Or, am I better off using APHS, for example, for the interpositive? I have already ruled out a slow sheet film for the interpositive because I can't afford 8x10 sheet film and have no means of enlarging 4x5. It seems that my choices are RC or APHS. Also, what you say about allowing the process to dictate the final result makes perfect sense.
     
  6. 2F/2F

    2F/2F Member

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    I just do it all on APHS using David Soemarko's LC-1 developer formula, and this leaves nothing to be desired. I can't see why you would want to use RC paper. For one thing, it's probably more expensive. For another, it is probably not as sharp as going film to film to film. It might be a way to introduce some exaggerated generation loss, if that's what you are after. Go ahead and experiment. It might be just perfect for what you are after.
     
  7. jmal

    jmal Member

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    2F/2F,

    Thanks for the response. Could you give some details about your process? I'll look into the LC-1 formula, but some starting times and any other tricks would be great.

    Oh, one reason for the RC interpositive is that you can burn/dodge to your taste and, assuming the detail transfers to the APHS, you get a "corrected" negative. Of course, I have no experience with this stuff, so I don't know how well it works.

    Jmal
     
  8. 2F/2F

    2F/2F Member

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    You can burn and dodge on the APHS as well, and that way you are truly contacting emulsion to emulsion when you go back to neg., while with RC, you're going through a layer of resin.

    You need four chemicals and water to make the developer. It consists of part A stock (alkaline developer), Part B stock (acidic restrainer), and part C, which is water. Part A has hydroquinone, metol, and sodium sulfite, 3g, 3g, and 60g, in one liter of solution, if my memory serves me correctly. Part B has sodium bisulfite, 10g per liter.

    You mix them together in an A:B:C ratio to equal 10 parts. Increasing part B in the ratio lowers contrast. If this causes uneven development, you increase part A in the ratio. For instance, say you start out with one liter at the standard 2:1:7 ratio, and your litho ends up too contrasty. So you add one part of part B, making it 2:2:6. Then your negs have the right contrast, but are mottled. So you try a 3:2:5 ratio.

    etc., etc. It is dirt cheap, keeps very well, especially once mixed into A:B:C, and is very consistent. Additionally, you can do zone-system-like placement and development with it.

    One thing that will help a lot, and be quite expensive, is a nice contact printing frame. I used to use a decent-quality picture frame that I had outfitted with anti-Newton's-ring glass and black backing paper, but now I use a real contact printing frame.
     
  9. Steve Smith

    Steve Smith Member

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    No. With RC paper the resin is under the emulsion not over the top of it. You wouldn't be able to process it if it was.


    Steve.
     
  10. 2F/2F

    2F/2F Member

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    Yes, you are right, Steve. Of course. What was I thinking?

    What I was getting at was that the texture of the RC is not smooth like litho film, so you don't get 100% positive emulsion to emulsion contact. The RC has a surface pattern.

    I guess if you get glossy surface it is. But you still have the paper base of the RC diffusing all the light. This may reduce sharpness.

    Now I feel like trying it.

    The trick will be learning how to print that glossy RC interpos just right to let you maintain all desired detail from the original neg, yet still transfer it to the final enlarged contact neg with the necessary contrast for the process you are doing. It will probably work quite well, but take a good deal of experimentation.

    I still think APHS and LC-1 would give you more control over contrast in the long run.
     
    Last edited by a moderator: Jul 24, 2008
  11. jmal

    jmal Member

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    Thanks for the info. In fact, I just ordered a contact frame from B&S a couple days ago. Once it arrives, I'll begin experimenting.

    Jmal