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  1. #61
    Athiril's Avatar
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    Not looking to replace C-41 with any of this, ideally what I want is two things from two different formulations:

    1) A large speed losing contrast increasing developer (would like the same amount of stops of range on the neg in a straight line but a steeper line.. ie reaching a higher dMax on the straight line), to only develop the fine grains and perhaps provide a solvent effect .

    2) The extreme other end. As useful as possible for underexposed images.

    Quote Originally Posted by Photo Engineer View Post
    Dan, very fine results and yes, I did know you were in AU. It was late at night here as you can see, and I wanted to kid you rather than post a long answer.

    I think that you have the problems ironed out. Just watch for the contrast difference. ECN is about 0.5 and regular C41 films run from 0.6 (pro films) to 0.75 (consumer films), and thus the color print materials and scanners are fooled by thinking that all negative films are C41.

    As for divided developer keeping, that remains to be seen. CDs oxidize more rapidly and are trickier to stabilize. You can make a B&W concentrate that lasts years, but CD kits are known to go bad rather quickly, even as a 3 part kit.

    PE
    Ignore the 'ideal' results, and think of the C-41 measured results as the ideal results, and compare those with the split-bath measured results, that shows hue shifting from the C-41 results.

    I will see what the gamma for the red, green and blue parts are to balance the grey scale vs the C-41 charts.. that should also be telling. If the gamma/contrast of one part (say green image) is significantly lower than the others for example, you may have prints with either green shadow cast or magenta highlight cast depending on printing.

    Quote Originally Posted by chuck94022 View Post
    Ok, this is all very cool. I don't understand it all, but it does seem that a divided C-41, while not perfect, is interesting.

    Allow me to ask the related question of divided developers: does the formula here result in working solution longevity similar to Diafine? Because it is divided, does it last "forever"?
    It does not last 'forever', last time I tried it a while ago, I found it stopped working after 6+ months, I don't know exactly when as I didn't use it very often (only a couple of rolls). I also mixed it up with tap water and no chelating agent.

    The other issue is iodide and bromide build up (in both bathes) and weakening of bath A from some development occurring, and dissolved silver build up from my addition of thiocyanate.

    Which may change developer characteristics with usage, my recommendation would be to replenish an arbitrary amount - it should theoretically self-balance to an equilibrium point.

    The preferred Bath A I would like to use, is with CD-4 with enough alkali to neutralise the H2SO4, and then HAS to set the desired pH, maybe with a weak alkali buffer to get an extra amount of HAS for better keeping properties.


    It is still quite economical, regardless of that, Flexicolor is also very economical, the cost is generally all in the bleach. One can be very economical in C-41 one-shot if they keep and replenish the bleach (and fixer too I suppose).

  2. #62
    chuck94022's Avatar
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    This became such an interesting thread to me, with a ton of useful information on what seems to be an accessible, useful alternative to standard C-41 processing for the tinkerer. Not perfect, but certainly usable. The benefits of brewing your own, plus more time/temperature tolerance, balanced against some potential color shift and possibly grain/speed changes, seem to make it something quite interesting to play with.

    Thanks Athiril (Dan) and PE for your contributions. Should this become a sticky thread?

  3. #63
    Photo Engineer's Avatar
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    Dan, quite frankly what bothers me is that the neutrals look good but the color balance is way shifted in the green example. So, they make good prints but with a different filter pack. Something odd is going on here.

    I have looked at and re-looked at those images. Oh, nothing suggests itself to me except that the images are exceptionally high in contrast compared to the original chart. Many steps missing in the neutral scale.

    Still thinking this out.

    PE

  4. #64
    Athiril's Avatar
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    I'll get my hands on some paper to try optically printing them and comparing at some point.

  5. #65
    Photo Engineer's Avatar
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    My early trials along "odd" lines of processing gave the same cyan results as yours did but with crossover consisting of low cyan dye contrast and high yellow dye contrast.

    Still Thinking this out.

    PE

  6. #66
    Athiril's Avatar
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    This may help:

    C-41 dye histogram (Gold 100 chart image), towards the right is increasing density (these are for the raw data, so the absolute values)




    Split-Bath (pic of Gold 100 @ 400 chart image)




    The yellow dye density range (dmax-dmin) is a little smaller in the split-bath image, magenta close to identical in dmax-dmin.

    The cyan dye dmax-dmin is smaller in the split-bath image, by the same amount.

    The magenta and cyan 'shapes' are a close match, the yellow 'shapes' the most different among the 3 but still bear some resemblance.
    Last edited by Athiril; 02-28-2013 at 11:41 PM. Click to view previous post history.

  7. #67
    Photo Engineer's Avatar
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    Dan;

    Something looks wrong with the hue of the dyes. Is that real?

    PE

  8. #68
    Athiril's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    Dan;

    Something looks wrong with the hue of the dyes. Is that real?

    PE
    These are just charts.. the hue is irrelevant, its just arbitrary values I chose to represent the cmy data, just so you can tell which is which. I just happened to colour them slightly differently

  9. #69
    Photo Engineer's Avatar
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    Well Dan, hue can vary due to the mask. If something goes awry, then the dye hues and mask color go off center.

    I'm still puzzled by some of that. I wish we could talk.

    PE

  10. #70
    Athiril's Avatar
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    The hues in the two charts are just colours I picked to colour them with, I did it by hand rather than numerically.

    They are not related to hue on the film other than to say "this part is representative of yellow dye density range".

    horizontal part is density, increases to the right.

    vertical part how much of that image in the related dye is that particular density.

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