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  1. #21
    Bill Burk's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    Paul Gilman showed that ISO 400 emulsions could be boosted to ISO 25,000 by appropriate reversal processing using heat. Grant found the same thing with negative heat processes.

    PE
    Wow, I thought that kind of speed boost required liquid nitrogen... like astrophotography work...

  2. #22

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    Reading Grant Haist's paragraphs again, he does not state the purpose of these reversal monobaths. He does state that "after light flashing and development, the final image consists of a contrasty positive image and a low-contrast negative image. The contrast of the positive is so high that for most purposes it is unnecessary to remove the negative silver."

    With modern films, I suspect we would need to experiment with the amount of thiosulfate. Too much, and you get an ordinary negative because too much halide was removed. Too little, and you get near-solid black. Also, I'd probably start with normal exposure, as boosting speed would probably make the whole process more unstable. Finally, development time will matter. Too long, and you get an ordinary negative. Too little, and you get black. Did somebody mention a tightrope?

    PE: Do you know why heat-reversal or heat-development boosts speed so much? 400 to 25000 is an enormous speed-up. Do you think this reversal monobath would (1) work at all, and (2) boost speed?

    Mark Overton

  3. #23
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    I have too have had no success with this. Have run Foma 400 and ORWO UN54 both were bracketed -2, -1, 0, +1, +2. Processed at 22degC for 90sec, then increased development time by 30sec for each subsequent test strip of film until I got to 6mins. I got results similar to Nicholas - all frames looked underexposed/under developed no matter what the development time was. Does Metol or hydroquinone go off even when stored with silica gel to keep out moisture? What puzzled me was I cannot even see the effects of the bracketing.

    To be sure I had not stuffed up exposing the film in camera I developed in HC110 for 7mins at 20degC and all fine.

    Other point was try as I might, I could not get a hint of reversal/fogging. Not even going to try to post sample images.

    Well I had a good day playing in the darkroom.
    Cheers - Andy C
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    16mm Cine, 35mm, 120, 5x4 & 7x5.

  4. #24
    Nicholas Lindan's Avatar
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    More cogitations as a result of my one unsuccessful experiment:

    As Mark Overton stated, the formula may have much too much thiosulfate. The formula given in Haist specifies 3-5 minutes for devloping time; my finding is that 4 minutes developing time is too long for ordinary B&W films and results in a negative image.

    Rating at 1/2 to 1/4 box speed may be a more appropriate starting point for bracketing.

    This technique will not produce pictoral results. I think the best one can hope for is a very high contrast positive with lots of fog. Haist even gives formula for using a bleach to get rid of the fog.

    I fear reversal monobaths may be a candidate for the first serious submission to the Journal of Irreproducible Results.
    Last edited by Nicholas Lindan; 06-02-2012 at 10:41 AM. Click to view previous post history.
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  5. #25
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    This isn't a special developer, it looks just like regular reversal just about.

    If you're not getting results, b&w bleach, wash, re-expose and develop and fix etc.

    Assuming your fixing in first bath is roughly more or less balanced.

    A weaker/underexposed image will give you a denser slide. Perhaps the right amount of fixing may balance that to a normal density range (as a positive), rather than overly dense.


    Quote Originally Posted by Photo Engineer View Post
    Paul Gilman showed that ISO 400 emulsions could be boosted to ISO 25,000 by appropriate reversal processing using heat. Grant found the same thing with negative heat processes.

    PE
    Is the description of the process in a book or online or somewhere available to read?
    Last edited by Athiril; 06-02-2012 at 07:41 AM. Click to view previous post history.

  6. #26
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    With the association to Itek, I wonder if this may have been used for reversal materials. Itek catered to the printing trade and this would be very important to them. I used a large quantity of various types of reversal materials for reproducing mainly very high contrast originals like engineering drawings and photographic line film. A few products reversed actinically but I think the other emulsions must have been designed for solarization to reverse the image. I first played with these around 1968 and remember some developers would not give a clean reversal. In the 1980's the products were much improved but using the film in a process camera, it was necessary to underexpose giving a bit of base density to retain details in drawings. Bleach would clean up the background without losing detail if you were careful.
    Richard

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  7. #27
    Nicholas Lindan's Avatar
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    The article in Haist mentions a 1890 account of achieving reversal using thiourea compounds, thiourea being urea with sulfur where the oxygen should be. As onions have a lot of pungent sulfur compounds, the same general reaction may have been the basis for the "Shallot Reversal Process":
    http://www.apug.org/forums/forum37/1...developer.html

    Although the Howell formula under discussion is described as "successfully used with higher speed films," it seems most of the activity with reversal monobaths was for processing microfilm and lithography film. May the reference have been to "high speed" Kodalith?
    Last edited by Nicholas Lindan; 06-02-2012 at 10:45 AM. Click to view previous post history.
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  8. #28
    Photo Engineer's Avatar
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    Paul Gilman's method was presented at the ICIS meeting in 2006 and is published in their journal. He showed real photographs which were projected transparencies. Kodak never investigated this process and little is known about the mechanism. A long thread is published here about it. Kodak rejected all solicitations to continue this work or to produce a trial run. So, the matter is dropped. AFAIK, there is a patent on this as well.

    Grant Haist moved on from monobath processes himself to develop "Bimat" used in space photography, and also to develop several thermally processed materials. He taught me how to coat them and I produced several examples myself using his method and similar methods. They produced negative images of normal speed though.

    PE

  9. #29
    Athiril's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    Paul Gilman's method was presented at the ICIS meeting in 2006 and is published in their journal. He showed real photographs which were projected transparencies. Kodak never investigated this process and little is known about the mechanism. A long thread is published here about it. Kodak rejected all solicitations to continue this work or to produce a trial run. So, the matter is dropped. AFAIK, there is a patent on this as well.

    Grant Haist moved on from monobath processes himself to develop "Bimat" used in space photography, and also to develop several thermally processed materials. He taught me how to coat them and I produced several examples myself using his method and similar methods. They produced negative images of normal speed though.

    PE
    If this could sensitise an otherwise ISO 400 speed film up to 25,600, wouldn't the same idea be able to applied to a ridiculously fine grain film.. such as on the level of Tech Pan or Vision Print etc, and give them much faster speed? Like 50D movie film @ 3200 ISO. ISO 25 films @ ISO 1600?

  10. #30
    Photo Engineer's Avatar
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    I cannot say as the experiments were never carried out.

    PE

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