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  1. #1
    kwmullet's Avatar
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    Interpositives v. direct positive/reversal for enlarged contact print negs

    Would anyone have some opinion/facts regarding the relative quality of enlarged contact printing negs made with interpositives as opposed to those made by a direct positive process with reversal processing?

    I've suspected that the potential of a process where you add a generation, such as when you contact-print a neg onto another piece of film to get an interpositive, then project that onto something like BPF200 to get your final contact printing negative is diminished compared to the potential of projecting the neg onto conventional negative film and reversal processing it for the contact printing negative.

    I'd like my suspicions to be wrong. I'd like to find out that adding an interpositive, if done correctly, was little or no negative effect on the potential of the final print, regardless of whether it's Azo or an alt process.

    After researching the reversal process, I haven't found a bleach recipe I'm really comfortable with. I'd like to hear from folks that have used the interpositive route to see if that's something that has as much potential as direct positive.

    Thanks,

    -KwM-

  2. #2

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    From what I have read at unblinkingeye.com part of it comes down to choosing developers for the interpositive and enlarged neg. http://unblinkingeye.com/Articles/En...nlargeneg.html

    In the article Negatives by Reversal http://unblinkingeye.com/Articles/NbyR/nbyr.html it notes that the primary difficulty with this technique is controlling contrast--special reversal films were usually recommended which are no longer available.

    I have not read anything mentioning much more. Certainly no, "this is better then that", procedure. One of the lady's here teaches a course in enlarged negs. Maybe she'll chime in.

  3. #3
    Jim Noel's Avatar
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    I have just finished teaching a workshop on this very subject.

    The making of an interpositive provides another level of control rather than the one provided by a direct positive negative.

    The interposiutive should be flat with full info in both the shadows and the highlights. From this positive, a new negative can be made with any desirable contrast range.

    I normally make 4x5 interpositives becaus they will fit into the enlarger which I use mnost often. Then they are printed to a new negative of whatever size I require at the time.
    [FONT=Comic Sans MS]Films NOT Dead - Just getting fixed![/FONT]

  4. #4

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    Good Morning,

    I agree with Jim. I have never seen the point of bothering with a direct reversal process when it's so easy simply to make a positive transparency from a negative. Not only is there the extra flexibilty gained by adjusting the exposure/processing of the positive, it's also easy to make, for example, 35mm positive slides from negatives of other formats or enlarged positives from small format originals; when the originals are on 120 or sheet film, it's also easy to do some cropping and still retain good quality.

    I did this years ago when I sometimes needed slides for classroom use or for some project in the graduate classes I was taking. At the time (this will date me a bit), I was using Kodak High Contrast Copy developed either in D-19 or Dektol 1:1; I assume that similar results would obtain with Tech Pan--if you can still find any at less highway-robbery prices. There is (was??) a Kodak film called Fine Grain Positive or Fine Grain Release Positive (never used it in 35mm) which was supposed to be good for making B & W slides. I do recall using that film, or something similar, to make 8 x 10 positives for use on an overhead projector. 8 x 10 Kodalith, by the way, also works similarly for that purpose if processed in highly-dilute paper developer.

    Konical

  5. #5
    Aggie's Avatar
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    Yep I teach this as well. Both Jim and Koni, I agree with. BTW I get to teach it this fall on the University level. Helps when the guy who first taught me darkroom techniques now has me coming back to teach with him instead of being the student.

    I find having the interpositive gives me more of a chance to tweak the negative into what I want. It's sort of (not exactly) like what we do to get the final print, only we use the result to make contact prints. I find it is fun to watch it all happen instead of having it in a tank and worrying if it turns out.
    Non Digital Diva

  6. #6
    kwmullet's Avatar
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    this is sounding good. I was hoping that my worries that (a) an additional generation of copy would reduce detail and "microcontrast" available in the final print and (b) that the base+fog of each generation of copy would diminish the potential for dynamic range would be fretting about nothing or at least making mountains out of anthills.

    Would I be correct in believing that the dynamic range of film so far outstrips that of any print (silver gelatin, azo, alternate) process that any B+F density you gain by having two generations of copies is a non-issue?

    -KwM-

  7. #7

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    KWMULLET, In my experience, with due diligence, your last statement is essentially correct. It might be frustrating at first, you will have to invest a fair amount of time and expense in materials to become comfortable in the process, but it is very rewarding.

    The lab I work at copies several million feet of motion picture film a year from b&w original negatives, interpositives and even projection gamma theatrical prints, so I feel pretty confident to say so.

    This is where having a wedge and a densitometry really comes in handy, but it is not essential. Since you will be dealing (I assume) with first generation negatives, the process won't be as tricky as say a 3rd generation 16mm reduction from 35mm release print negative printed on release print stock.

    Good luck

  8. #8
    Aggie's Avatar
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    Quakecon is the first week in August. I may accompany my son down there to Dallas. If so I will bring my stuff and teach you how to do it. Just depends on if I want to spend 22 hours driving one way with my son and his invariable exhaust in a closed up vehicle not just once, but both ways.
    Non Digital Diva

  9. #9
    kwmullet's Avatar
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    very cool, Aggie. Even if you don't have time for a tutorial, we need to hook up and have coffee.

  10. #10

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    Good Afternoon, KWM,

    Kino is correct, except that I don't think making B & W transparencies from original B & W negatives is necessarily either very frustating, time-consuming, or expensive, assuming that you are already familiar with basic darkroom processing. The learning curve is not, in my opinion, a very steep one, but I've had no experience with anything except original negatives from 35mm to 4 x 5 in size.

    Ahead of any "tutorial" you may receive, you might prepare a simple apparatus to hold your originals (enlarger negative carriers and/or a copy stand can be an obvious part of it) and a lighting arrangement which will provide smooth, even lighting behind the negatives. If you're going to make 35mm slides, a slide-duplicating attachment or a macro lens would simplify things.

    Konical

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