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  1. #71
    htmlguru4242's Avatar
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    AgX, that patent link is great; pretty much exactly what we've all been talking about.

    And, ZorkiKat, I like the idea of having Ilford coat HP5 on a Reseau :-P.

    But, in all seriousness, I wonder if it would be possible to have them (or someone) do it?

  2. #72
    AgX
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    Correction

    Quote Originally Posted by AgX View Post
    As to my understanding the Polachrome films are made this way:

    Clear base (through which the film is exposed)
    Additive line grid
    Receptive layer (containing fogging agents)
    Sensitive layer (high gammy and Dmax)

    As fogging agents are per definition substances which cause fogging due to their impact on silver halide crystals, those agents I had in mind should rather be called nuclei-forming substances, as the silver halides (made soluble by fixer complexing) diffusing into the receptive layer are ionic, and it is these ions that take part in the development process which is started at nuclei formed by solid metals incorporated in the receptive layer.

  3. #73
    AgX
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    another correction…

    Quote Originally Posted by AgX View Post
    The typical structure of these [additive films with a filter grid] are base, (ortho-)panchromatic emulsion, grid.

    Of course this is nonsense concerning the two most famous materials with integrated screens…
    For those it must rather be: base, screen, emulsion

    Though a screen on the emulsion would have made production then more flexible. And of course would made obsolete that focussing issue. (One could overcome this with plates and springbacks by inserting a plain plate while focussing.) Those systems employing a separate screen on the emulsion had rather the issue of negative/positive processing as primary goal on mind.

    With the Agfa Farbenplatte (and later the film based version) the problem is obvious. A closed resin layer on top of the emulsion would hamper processing. For the Autochrome with those starch globuli the cause might the process of transferring those, or difficulties in enclosing them within a protecting gelatin layer. I don’t know.

    (Interesting: I don’t remember to have found any reference by Polaroid for their Polachrome films to that difference in focus…)

  4. #74
    Martin Reed's Avatar
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    [QUOTE=Roger Hicks;478427]Dunno. If he does, blame me. Martin is incredibly enthusiastic and knowledgeable, but also, as the fons et origo of Silverprint, incredibly busy. If he has the time, I'm sure he'll respond in detail. If he's too busy, he'll probably say so unless he's WAY too busy. Either way, he's an incredibly nice, straightforward, honest guy.

    Blimey, what an introduction! Sorry for late reply, I've only just found this thread. Briefly, as I'm about to leave the building, I did indeed have a crack at Autochrome, out of interest & as subject for an article in Ag. I found out enough to know that it could be recreated, but would take immense funds, and the remainder of one's life. I got as close as just barely recovering some colour information from dyed starch grains, applied to a glass plate, and using FP4 as the recording medium. The only starch that is suitable is potato starch - no other starch particles will hold enough dye, and even potato starch contains only a small percentage of suitably large grains. Add to that the problems of masking the gaps between the particles with carbon, the pressure required to flatten the package, and coating with a suitable panchro emulsion. That the Lumieres managed to make such an unwieldy process work at all was an immense achievement. It was of it's time & will never be repeated, so let's enjoy the body of work that was made with it.

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