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  1. #501

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    Quote Originally Posted by Alan Johnson View Post
    It is usually considered that it is the ascorbate which is used up, as reported by Gainer:
    http://unblinkingeye.com/Articles/Sy...synergism.html
    At the end of that article, Gainer recommends an ascorbicacid/phenidone ratio of at least 80:1, and says that an excess above that "serves as a preservative and as a reserve." The ratio in my formula is 148, so it should have considerable reserve of ascorbic acid.

    D316 also has .05 g/L of Phenidone, but less ascorbic acid. Have you developed a 36-shot roll in D316? If so, do you recall how many ml of dev you mixed?

    Mark Overton

  2. #502

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    Mark,

    I have not done the test that you report where density is compared for a short test strip and for a 36 exposure roll.
    But I have developed 36 exposure rolls using 10ml of D316 in 500ml sulfite solution.
    The required time was about 2.5 times the Xtol 1+0 time.This is not a reliable figure as I used my classic cameras,but it might do for a start.

  3. #503
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    Mark;

    That is not a classic upswept curve. It s a normal curve, but underexposed or underdeveloped by about one or two stops. My guess would be underexposure at this time. So, we are just looking at toe, no mid range or shoulder.

    The ratio you use is too high and with a full roll of film, the PD is being exhausted.

    That is my guesstimate at this time.

    PE

  4. #504

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    Quote Originally Posted by Photo Engineer View Post
    That is not a classic upswept curve. It s a normal curve, but underexposed or underdeveloped by about one or two stops. My guess would be underexposure at this time. So, we are just looking at toe, no mid range or shoulder.
    Ron, the left end of the toe in that chart has positive slope (not flat), which tells me that I overexposed a little. Kodak's curves start flat. That leaves the option of underdevelopment, and given that the leader's density was only 2.7, I believe it. BTW, what density should a typical leader be?

    Quote Originally Posted by Photo Engineer View Post
    The ratio you use is too high and with a full roll of film, the PD is being exhausted.
    That is my guesstimate at this time.
    Would reducing the amount of ascorbic acid (thus reducing the AA/phen ratio) help this exhaustion problem? Or is the only cure to add more phenidone?

    Your knowledge is appreciated as always!

    Mark Overton

  5. #505
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    Mark;

    The maximum density of any film is based on design. Most films try to achieve a Dmax of 3.0 or thereabouts and a Dmin of 0.1 or thereabouts. Overexposure of a piece of leader can actually reduce the maximum achievable density in some films due to "solarization" from the extreme overexposure they sometimes get.

    I revise what I said. The film is probably both underexposed and underdeveloped. Try to get a contrast in the mid tones of about 0.6 - 0.8.

    Use of less AA will make the problem worse, not better. The solution is to increase PD.

    PE

  6. #506
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    Quote Originally Posted by albada View Post
    Does developing a roll of film destroy a certain number of milligrams of developer? I'm still investigating why test-strips are denser than a roll. That happens with both the Dimezone S formula above, and the Phenidone formula below:
    Yes developer is used up and exhausted by processing a single film particularly when the level of dev agents is low and dilute.

    At the level of Phenidone you have in the second dev 0.05g/l your at equivalent of a PQ version of D76/ID-11 diluted 1+3 and if there's insufficient volume you will be exhausting the developer with a whole film and would get reduced Dmax and contrast. A test strip in fresh dev would suffer no exhaustion and would need a shorter dev time as well.

    There's an Ilford reserach article published in the 1950's which discusses the exhaustion rates I'll dig out the details,

    Ian
    Last edited by Ian Grant; 03-13-2012 at 03:40 AM. Click to view previous post history.

  7. #507
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    Mark a rough guide is as follows based on 1955 data:

    1g Ag (12 120 films) uses 1.6g Metol or 0.16g Phenidone. - so the exhaustion rate is roughly 0.016g Phenidone per fully developed film.

    Sodium sulfite 48 g
    Ascorbic acid 7.4 g
    Sodium metaborate 4.2 g
    Phenidone 0.05 g

    So a Tank with 300ml or 500ml of this dev only contains 0.013g (300ml) or 0.025g (500ml) of Phenidone - this is why you're having problems. This also shows clearly why a test strip is OK but a full film has exhausted the developer before full development takes place.

    Here are more details of developer exhaustion I gave in a post 18 months ago.

    Ian
    Last edited by Ian Grant; 03-13-2012 at 09:03 AM. Click to view previous post history. Reason: ad link

  8. #508
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    i'm very interested in seeing this research article.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  9. #509

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    Quote Originally Posted by Ian Grant View Post
    Mark a rough guide is as follows based on 1955 data:

    1g Ag (12 120 films) uses 1.6g Metol or 0.16g Phenidone. - so the exhaustion rate is roughly 0.016g Phenidone per fully developed film.
    Your 1955 data suggests that the phenidone is not regenerated?

  10. #510

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    Ian, this is very helpful! Thanks for posting it. I had no idea at what rate Phenidone was consumed/destroyed.

    A 24-shot roll in a Paterson tank (325 ml) will have twice as much developer available per frame compared to a 36-shot roll in a stainless tank (220 ml). We want both to develop to similar densities, so this is an important issue.

    One question: Pat Gainer's PC-TEA uses only .05 g/L of Phenidone, which is the same as my formula. So I'm wondering: Do folks have trouble with exhaustion with PC-TEA?

    Mark Overton



 

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