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  1. #431

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    Quote Originally Posted by Photo Engineer View Post
    Besides, if you slide curves around, as I noted earlier, then you can do the sliding for speed, curve shape, and B+F or minus B+F just by sliding the two sheets of paper. PE
    In my graphs 8 postings ago, I slid the curves around (by removing Dmin) to show that:

    1. Re-fixing boosted the slope of Acros.
    2. Re-fixing changed (and improved) the shape of TMY2.

    Why would re-fixing boost slope? Perhaps there was retained silver in thinner areas, as well as retained dye?

    Mark Overton

  2. #432

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    Quote Originally Posted by Photo Engineer View Post
    Michael;

    The paper sees the base + fog, and so lets exaggerate this situation to 2 films with a Dmin of 0.2 and 1.0 respectively. Since they are vastly different, you would not print the foggy one at all. Subtracting PE
    I'd agree in a case like this because something is clearly wrong with a Dmin of 1.0. But if we have normal levels of fog for both films (each being different back to my Delta/TMX example), what difference does a longer printing time (within reason of course) make? If the Dmin levels are normal, so that we have no issues with image structure characteristics in the negatives etc, if two films have identical plots for net density (gross minus Dmin), as long as the printing exposure is increased for the film with higher Dmin, the macro gradation in the resulting prints should be identical. Sorry if I'm being repetitive but I'm still not quite following. I suppose one might ask "how do we know what Dmin is normal for a given film/processing combination?". But plotting gross density doesn't answer that question.

    Mark - apologies for sidetracking the thread. I am just as curious about your question!

  3. #433
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    Michael;

    We are in a thread on the design of developers and fog is a critical issue (along with curve shape, Dmax, Dmin, and etc....) so we must see all aspect of the curve. This is R&D here not a game. We ned to see all of the data.

    Mark;

    Fixing or re-fixing can change tone, or the color of the Dmin can change.

    PE

  4. #434

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    Quote Originally Posted by Photo Engineer View Post
    Fixing or re-fixing can change tone, or the color of the Dmin can change. PE
    I got the Dmin numbers:
    Before re-fixing the TMY2 (ie, with magenta cast), Dmin = 0.40.
    After re-fixing, Dmin = 0.26, which is typical of this film.
    That's a drop of 0.14. Visually, I'd say the removal of the dye can explain this entire drop.

    @Michael: There's no problem about discussing inclusion of B+F in graphs. I just didn't want my question about slope-change to be forgotten.

    Mark

  5. #435

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    Mark - is the Dmin of 0.26 with your developer or XTOL? Just asking because I usually get slightly lower Dmin with TMax films with XTOL (and other developers). Usually 0.20 +/-.02. Then again it could just be a difference in densitometers.

    PE - understood. Certainly not trying to imply it is a game. I doubt you will find too many people who take film/developer testing as seriously as I do. Apologies for the digression.
    Last edited by Michael R 1974; 01-09-2013 at 08:07 AM. Click to view previous post history.

  6. #436
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    Michael, apologies to you and others. I know that to some people, the quality of their developers or processing is not a serious proposition. I myself take it very seriously and do my measurements to the same standards I used at EK. This actually included B+F or with Dmin and without B+F depending on the purposes of the work.

    My work area is messy, but very very well equipped. I even graph on Kodak paper as can be seen in some of my posts. I''m used to making my measurements and calculations from those curves.

    PE

  7. #437

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    Quote Originally Posted by Michael R 1974 View Post
    Mark - is the Dmin of 0.26 with your developer or XTOL? Just asking because I usually get slightly lower Dmin with TMax films with XTOL (and other developers). Usually 0.20 +/-.02. Then again it could just be a difference in densitometers.
    The TMY2 Dmin of 0.26 is with my developer, D316. XTOL consistently gives me a Dmin of 0.25. Yes, I think this could be a difference in our densitometers. One of them could have a slight nonlinearity around the calibration-setting for pure white.

    Mark

  8. #438

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    D316 is a two-part developer consisting of sodium sulfite powder and a liquid concentrate. I'm finding that it's convenient to measure both by weight. Electronic scales are cheap. Search on amazon for "scale .01g". They typically cost about $15, and work well in my experience. That's the cost of just three rolls of film. At that cost, there's no excuse for a darkroom to not have one. To mix this dev:

    1. Put a plastic beaker on the scale and press Tare to zero it.
    2. Pour in the correct weight of liquid.
    3. Press Tare to re-zero the scale.
    4. Pour in the correct weight of sulfite.
    5. Add water to fill-line and stir for 3.5 minutes to dissolve.

    D316 weighs 22.8 grams/litre. And you need 45 grams/litre of sulfite. So to make 250 ml of dev, pour out 5.7 g of liquid and 11.3 g of sulfite.

    I prefer to do this than deal with air in bottles of XTOL plus the initial mixing of 5L of XTOL. All things considered, D316 is not much less convenient than XTOL. It's fine for occasional shooters of 1-2 rolls/month for whom the few extra minutes of measuring and stirring won't matter.

    Mark Overton

  9. #439
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    Mark;

    I'll bet that some would find it convenient to have the formula and the mixing instructions in one long post that they can cut and paste for their lab. Could you please do that.

    I know it would be nice for my own work.

    Thanks.

    PE

  10. #440

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    Quote Originally Posted by Photo Engineer View Post
    Michael, apologies to you and others. I know that to some people, the quality of their developers or processing is not a serious proposition. I myself take it very seriously and do my measurements to the same standards I used at EK. This actually included B+F or with Dmin and without B+F depending on the purposes of the work.

    My work area is messy, but very very well equipped. I even graph on Kodak paper as can be seen in some of my posts. I''m used to making my measurements and calculations from those curves.

    PE
    I get it, but when you say we're doing "R&D" here, I have to disagree a little. The H&D curves are not being generated from contacting, granularity and acutance are not being measured using microdensitometry etc. So all things considered, plotting net density is probably a relatively minor source of error if at all. Anyhow, onward and foward as they say.



 

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