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  1. #21
    polyglot's Avatar
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    OK, scans. Two DNG files [url=http://www.brodie-tyrrell.org/apug/ra4-troubles/]here[url], not much difference between them. Both from VueScan 9.0.94, Nikon 8000, RGB gain=2, 24 bit 150dpi.

    Reference:
    - Portra 160 at about EI80
    - primary illumination is flash from softbox
    - developed by a pro lab
    - scans and prints fine
    - I have a practically identical version developed at home, also scans and prints fine but with slightly different filter pack

    Difficult:
    - the baby photo linked earlier
    - Portra 160 at about EI100
    - primary illumination is flash from softbox
    - developed with Fuji Hunt 5L kit
    - scans fine
    - horrible prints linked earlier

    There's more dynamic range in the former, but it all disappears when printed of course. I will be retrying the latter when I get a couple consecutive hours spare now that I have a little more practice and some definitely-successful prints from other films.

  2. #22
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    They've been post-processed, so I cannot tell anything from the histograms.

  3. #23
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    They're raw DNG scans. No processing. If I open them in VueScan as "Image", then they appear as negatives - they've had no inversion or anything.

  4. #24
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    They've been post-pro'ed by vuescan, colour balanced and levels. Both images are using the whole histogram range almost. I doubt your negs are much above a dMax of 2.0, let alone 4. I don't think your negs are filling the entire range of the scanner.

    Given that, I can't infer any relative density range differences.



    Other option would be to take readings directly through the film.

  5. #25

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    The filter pack is 15M 10Y, which seems a little on the cyan side.
    I don't know about the rest but your starting filter pack seems a little off to me. The usual recommendation is to start with a filter pack of 0C, 45Y, 45M, run a test strip to determine exposure and once the exposure is determined to adjust the filter pack to eliminate any color cast. My final filter pack is (usually) 0, 45, 55 with CA.

    Thomas
    Thomas

    No art passes our conscience in the way that film does, and goes directly to our feelings, deep down into the dark rooms of our souls.
    — Ingmar Bergman

  6. #26
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    I have a breakthrough: separate bleach and fix do not work properly, at least for me and the (Kodak Ektacolor RT) chemicals that I'm using. I do not know why, but I attach here my test strips demonstrating the problem. It looks like the fixer is catalysing the bleach in some way and that bleaching does not go to completion unless the fixer is present. Perhaps there is a buffering agent in the fixer half that is required to let the bleach half work properly.

    Blix (according to CIS-49 and J-39) is made up of 14% fixer and 20% bleach, the rest water. My assumption was that if I made up a 20% mix of bleach, a 14% mix of fixer and used them sequentially, it would work the same. The total volume is doubled (there are, after all, two baths now) and the concentration of each chemical in its own bath is the same as what it would be in the blix. Ektacolor instructions say 0:45-1:00 of time for blix, so I've been running them for 1:00.



    In order from left to right (pay attention to the saturation in the yellow rose):
    Strip A: is cut from a whole print made with separate bleach+fix (older working solutions, 20%B then 14%F)
    Strip B: strip made with pretty-exhausted blix at official strength (20%B+14%F)
    Strip C: new strip made with separate bleach+fix (brand new solutions, 20%B then 14%F)
    Strip D: new strip made by combining separates to form 50%-diluted blix (10%B+7%F), 2:00 process
    Strip E: new strip made with separate bleach+fix, longer process time (20%B then 14%F), 2:00+1:15 process

    It went down like this. I made up a small quantity of blix (at proper strength) when I was starting out and have been using that to do test strips. I also made up separate bleach and fix working solutions and used them to make final prints. I've been replenishing the latter and let the former just run out / exhaust. I noticed however that a print I made (strip A) had a bleach-bypass look to it compared to the test strip (B). Thought "that's cool, I'll keep that" then "shit I'm under-replenishing the bleach". So I did a big replenish... no change. And tried again with brand-new solutions from my pre-mixed replenishment bottles (strip C): no change. Here's where the panic sets in: has my separate bleach and fix died in the bottle? How does bleach die in 2 weeks in a PETE bottle? No way.

    So I got some of my separate bleach and fix and mixed them together to form a blix that's half the recommended strength and ran it for twice as long (because of the low concentration). Perfect results (strip D). Then to check whether the longer run was the solution, I did it again with separates, gave the bleach 2:00 and found that it didn't work (strip E).

    Conclusions:
    - blix works as advertised
    - doing separate bleach and fix results in a mild bleach-bypass effect
    - bleaching for longer doesn't improve the situation
    - mixing a more-dilute blix and running it longer works fine

    The last point is useful for me because I mixed up 1.5L of separate bleach and fix at their respective recommended dilutions. Combining them gives a 50% dilution from recommended and I'd rather use it than bin it.

    Looks like I have a couple of prints to re-do! Fingers crossed, this might even solve my can't-print-a-portrait issues. Update in a few more days.

  7. #27
    Photo Engineer's Avatar
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    The bleach and fix portions of the blix were designed to work together in conjunction with each other. If separated, they will give the results you show. It is retained silver and is akin to bleach bypass. See the reduced saturation in the reads and yellows?

    PE

  8. #28
    polyglot's Avatar
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    Certainly seems so, PE. Does one need to buy different chemistry to use separately as you suggest in post #7?

    At least I have a repeatable way of generating the effect when desired!

  9. #29
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    I suggest that you use a real, 2 part blix designed for paper. That is best.

    PE

  10. #30

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    Dear polyglot.

    I’m not completely sure about, but I suspect an elevated pH in the bleaching solution if the “Fixer part” is missing. The “Fixer part” usually/often contains sodiumbisulfite and/or acetic acid to maintain a acidic milieu. Depending on used product the pH of the complete Blix should be slightly acidic around pH 5.5 till about 6.

    Maybe a bleach accelerating Agent is missing too (something like mercaptotriazole), but this would be more for film blixes, I think…

    Kodak RT BLIX works fine if the original “Fixer Part” is substituted by a liquid acidic BW Fixer (Tetenal Superfix). This Superfix does (naturally) NOT contain bleach accelerators or silver solvents, but shifts the pH to the acidic side and boosts bleaching activity.
    If you wanna stay with separated Bathes (without having separated solutions designated for this) I would simply try to add some acetic acid (in increments) to your bleach and watch it’s activity.

    Hypothetical: Try to omit the rinse step after (a boosted) stop bath (add about 10-20g sodiumbisulfite per Liter to your 2% acetic acid. More free acid and makes developer residues soluble. Caution, irritating sulfur fumes may release).
    The inherited acid in the drum (you do drum processing, don’t you?) could be enough to lower the pH the necessary bit in the following bleach step.

    Or simply stay with the original BLIX solution, this would save time and trouble …

    Regards, Stefan
    Last edited by stefan4u; 07-10-2012 at 09:06 AM. Click to view previous post history. Reason: typo(s)

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