Best mothod for making Large format +ve's from 6x7 negs ? ?

Discussion in 'B&W: Film, Paper, Chemistry' started by nick mulder, Nov 27, 2005.

  1. nick mulder

    nick mulder Subscriber

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    Hi,

    I've got a few 6x7 B&W negs I wish to see printed in ~8x10 polymer gravure prints -

    I have been trying to create interpositives for this process by simply enlarging the 6x7s directly onto Ilford Delta 100 4x5 negs as I had some on hand and wanted to test before I spend bigger bucks on the 8x10...

    I chose an original 6x7 neg for the test that had a good range between black and clear - in my first attempt I stopped the enlarger lens down to f32 and ran 10 steps each 1 second in duration - the +ve turned out black with only some discernable detail upon close inspection and a hint of any difference in the exposure times around the 1 second band -

    Upon the second attempt I exposed for an 'instant' at f32 again (enough to get the bulb up to full brightness and then fade again) - this time round I got an image that could be seen - however its contrast was greatly reduced, way below that of the negative... (rodinol 1:25 in all cases btw..)

    I am sure the darkroom is light tight and I have made sure the enlarger is not spilling excess light out of its sides when on (its covered in darkcloth in the right places) - i am making fine prints from the same neg in the same night also ...

    For what i wish to do with the photopolymer i need a +ve with much more contrast than i have achieved ...

    I might try using some ND on the enlarger and pushing the film next, but until tomorrow night >> any ideas as to why the reduction in contrast, how to increase it or simply another way to do this ?

    cheers as always,

    nick
     
  2. eumenius

    eumenius Member

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    Hi Nick,

    the usual negative film is not really suitable for such kind of interpositive making due to its high sensitivity, relatively low contrast and isopanchromatic sensibilisation. The reduced contrast you get can be accounted for an overall fogging of your film. There are special films made for purpose - like some sheet lith films, or I know Russian MZ-3L film (unavailable in NZ, of course). They're quite slow, just like paper, and have either ortho or no sensibilisation - just an extra-finegrain emulsion on a clear transparent base, and you work with it like with paper. They also yield high maximum densities, what's preferred sometimes in contact processes. As I can understand, Delta will just not fit your task :sad:

    There also are line-art films for typesetting devices, low-speed and high-contrast - you can try to use it, but you would need to find the means to cope with high contrast of these by right soft development. But maybe your photopolymer technique requires high contrast? In this case a typesetting machine film will do.

    Cheers from Moscow,
    Zhenya
     
  3. David H. Bebbington

    David H. Bebbington Inactive

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    When trying to make projection transparencies from MF b+w negs, I used Ilford Ortho sheet film and Ilford Phenisol developer (couldn't get enough contrast with Ilford PQ Universal dev.).
     
  4. eumenius

    eumenius Member

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    Yes, Ortho film is a copy film with right properties in terms of Dmax and ortho sensibilisation, and it should be contrasty - so maybe it's a choice. But I am not sure it's available in big sizes? Here in Russia we don't have it at all :sad:

     
  5. nick mulder

    nick mulder Subscriber

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    I find that higher contrast in photopolymer +ve's yield solarplates that are easier to ink up and the prints have an almost half comic-strip/half realism effect that I really like ...

    Do these films keep any tonality tho ? hmmm, maybe halftone screens ?

    In any case, any links to sites that stock this film that will ship internationally would be good - (i order most film in bulk over the net anyway)
    :cool:

    thanks Zhenya,

    nice to see others here at APUG at this time of the Earths rotation (;
     
  6. nick mulder

    nick mulder Subscriber

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  7. eumenius

    eumenius Member

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    Yes, in this case high contrast copy/typesetter line film will do :smile: The tonality will be preserved, if you don't develop it in its dedicated hi-contrast boiling caustic developer, intended to make fine rastered dots in half-tone colour separated pictures...

    Halftone screens will be too much, I think - I am sure you'll get fine results just with the film, with no raster. And the resulting pictures won't look like a newspaper :smile:

    I'll try to find some links for you - but I've never ordered anything in your fashion, it's impossible in Russia :sad:

    Acros Ortho film is something I would love to try by myself, and I think it will work for you, too (if it's slow enough) - but I didn't use it, it's unavailable here, as well as Ilford Ortho :sad: Anyway, you'll be always able to shoot some nice portraits with it! :smile:

    Nice to see you here, too - I always had the same problem with APUG, everyone usually sleeps when I'm up :smile:

    Cheers,
    Zhenya

     
  8. David H. Bebbington

    David H. Bebbington Inactive

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    Ilford Ortho used to be available in sizes up to 10x12" - don't know about post-receivership and the position in other countries. It should be possible to get some kind of high-contrast film (such as blue-sensitive "line" film), if developer is a problem and you don't want to make your own, an X-ray developer should give the necessary contrast.
     
  9. Peter Schrager

    Peter Schrager Subscriber

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    Films

    Nick-try Freestyle. They have some nice films. Bergger BPF18, Maco Genius film.
    Try using HC-110 or eqivalent for developing. For the interneg I use it at 1:19
    and for the positive at 1:4 to 1:9.This is for negatives for platinum. Longer devlopment =contrastier negatives. Not very hard to do . You will be able to use a red filterin the darkroom. Some people are using the Frestyle APHS film also. There is an article on unblinkingeye about this.
    Peter
     
  10. Ole

    Ole Moderator Staff Member Moderator

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    "Used to be available"...

    I have two boxes (100 sheets/box) of Agfa Gevarex 24x30cm, a variable contrast copying film. It works fine in camera, too - at EI 6.

    Copy film is still available though - MACO, Ilford, Tasma all make anything you could need for any contrast.
     
  11. Claire Senft

    Claire Senft Member

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    I know extremely little about your process. That however will not stop me from making a sugesstion.

    Why not use a very high contrast grade of RC glossy paper, do all of your dodging and buring and use it a paper positive?
     
  12. nick mulder

    nick mulder Subscriber

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    I too thought of this as an option - solarplate isnt the cheapest thing to test things out on but I may ask for an offcut to try this ...

    it needs about 15 or so secs in full sunlight or 20 secs on a partially cloud obscured sun to get a good exposure - unsure of the effects of a longer one - will be interesting to find out
     
  13. nick mulder

    nick mulder Subscriber

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  14. Aggie

    Aggie Member

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    I have gotten the interpositive and subsequent enlarged negative down to a a workable format. First use the ortho film for botht he interpositive and the larger neg. Use Dektol to develop the film. Controling contrast is where you have to work with a more dilute solution of dektol and prefogging of the film. The interpositive needs to be flat, with what looks like not very much contrast. When you make the negative, you can then add the contrast back in. Trust me it does happen. I have done hundreds of these enlarged negs. Some from 35mm up to 8x10, some 4.5x6 up to 8x10 and quite a few 6x7 up to 8x10. The only other equipment you need is a 4x5 film holder and an 8x10 film holder. You do the development in the darkroom under regular yeloow safelights. This affords you the ability to see what is happening with the negatives. The only thing I would suggest in this set up is adding some old rc paper that after developing you would have thrown away. I place these sheets at the bottom of the developing trays to better be able to see what the neg is looking like. If you want more info, PM I wll find some of my enlarged negs and post them later.
     
  15. nick mulder

    nick mulder Subscriber

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    sounds good, I'm actually after a higher contrast interpositive tho as its for solarplates so the neg wouldnt be required, however I guess I could do some pt/pl prints from 6x7 in the larger size - firstly tho, what would you change in your process to achieve a higher contrast +ve ?