Negative + negative = Positive

Discussion in 'B&W: Film, Paper, Chemistry' started by modafoto, Jul 7, 2005.

  1. modafoto

    modafoto Subscriber

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    Hi

    I have just developed a roll of APX100 on which I have copied several negs and the result was hoped to be some ok BW slides. I bracketed a lot as it was an experiment. I developed the film normally in Rodinal 1+50 for 13 minutes and the slides turned out a bit thin...so I will expose a bit more next time. The contrast is low so more development next time, too.
    The base color is just a charming thing for me. Gives the slide a great effect.

    Any recommendation or comments are very welcome.

    Morten
     
  2. Claude

    Claude Member

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  3. modafoto

    modafoto Subscriber

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    Thanks for the link.

    I have considered doing direct positive development, but I can't get hold of the chemicals in Denmark (unless I am willing to buy 25 kg. of each chem). If I get hold of the chemicals some day I will try it.

    Any danes here with knowledge on how to get chemicals?

    Morten
     
  4. Claire Senft

    Claire Senft Member

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    For those that are low in contrast why not try intensifiying in 1:4 selenium?
     
  5. John Cook

    John Cook Member

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    Just some technical thoughts.

    The H&D Curve is a curve - not a straight line. This is an indication that negatives are not a linear (albeit reversed) representation of the original scene, but rather a distortion of it.

    Your positive copy negatives of the original film therefore represent a distortion of the distortion. The effect is that both nearly white and nearly black values will each be flattened, compressed and difficult to distinguish.

    In addition, paper "sees" only about 2-1/2 stops of light from the enlarger. The film, on average, "sees" a subject brightness range of about 7 stops.

    Negatives, developed normally, are therefore much flatter than reality in order to be printable. A positive film shot of a flat negative will be flatter than a paper print from that original negative.

    As you increase development to increase contrast, some of the loss of tones in the toe and shoulder will tend to be aggravated. Thus, the invention of special copy films (which may or may not still be offered by Kodak).
     
  6. modafoto

    modafoto Subscriber

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    Thanks for your answer. I realize that my method will not be the best, but as an experiment it is fun, as I might get something I like without knowing that I wanted it :smile:

    If I was to make great copies of negs (or slides from negs) I would choose a copy film.

    Morten
     
  7. titrisol

    titrisol Member

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    once again I wonder is microfilm (copex rapid) or similar would help.
    They have clear base and extra-fine-grain :wink:
     
  8. Tom A

    Tom A Member

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    Hi Morten

    I am living in Denmark and I have been experimenting with Ilfords process for making B&W transparencies directly from normal B&W-film for the last month or sow. I know of your problems with raw-chemicals. But instead of buying the chemical by a grosserer in Denmark, in large quantities I bought some of the chemicals in Germany at:
    Brenner
    Kaliummetabisulphit (Potassium-)
    Kaliumpermangenat (Potassium-)

    Natriumthiosulfat (Sodium-), I bought through a friend, as Brenner did not have it in stock at that time.

    Concentrated sulphuric acid I got at my work, where we have a lab. I have not tried to find sulphuric acid in shops. Maybe well equipped paintshops can get it for you, or the local auto mechanic may have some for refilling car batteries.

    As the developer I use Tetenal Variospeed W, but in principal you can use any paper-developer.
    You just have to find your own developer times as it may vary between the different developers.

    For my process and a 36 exp. Pan F @ 50 iso, I use.

    First developer:
    50ml of Variospeed W
    90ml stock solution of natriumthiosulfat (sodium-), (20 grams of natriumthiosulfat dissolved in 1000ml of water)
    Tap water to 320ml.
    Time in 1. developer 12 minutes @ 20 degree C (Const. agitation the first 30 sec then 2 kips every 30sec)

    The used first developer is reused for the second development, and then dumped.

    For the other solutions I use Ilfords recommendation.

    The other films I have done experiments with, are EFKE 25 and MACO IR820c. Where EFKE 25 is my favourite film and for the MACO I’m still working on finding the optimum concentration of natriumthiosulfat.

    The transparencies from the process are absolutely beautiful, the blacks are BLACK and there are lots of greys in the pictures :smile:
    Pan F ends up with plenty of contrast when developed for 50 iso, lower the time in first and second developer for pictures with less contrast (and speed).
    EFKE 25 gives really nice greys and beautiful blacks, with Variospeed W, it has a nice warm tone. I still have to try other developer to see if they give another tone.

    I hope this information will help you.

    Tom A
     
  9. Jordan

    Jordan Member

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    Tom, thanks for the info on Efke 25 reversal processing. I have a lot of Efke 25 and have wanted to try that.

    Morten, copying negatives is a good way of making B&W slides (see http://www.photosensitive.ca/BWslides.shtml at my site) The film usually used for this purpose is Kodak 5302, a fine-grained, blue-sensitive negative film designed for making positive 'prints' of B&W movie film negatives. I develop the film in working-strength Ilford Multigrade paper developer to get nice contrasty slides. If you have a slide-duplicating attachment or macro lens of good optical quality you'll get good 'snappy' slides. When I need quick B&W slides this is the method I use.

    Other people have used Tech Pan for this purpose as well, but it is expensive (and discontinued). Kodak 5302 can be hard to find, but it is used for electron microscopy, so a scientific supply house should sell it. It is sold in 100-foot rolls quite cheaply (US$16 when I bought mine).