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  1. #101

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    my statement still stands. ALL THINGS BEING EQUAL the extra 1.5 gr of metol in thorton's does yield a negative of greater contrast. that is why Thornton modified the Stoeckler two bath. Rudeofus is right in saying that Stoekler is a low contrast developer. Dave Allen is right for asserting that Thornton's two bath is "is no more a low contrast developer than many others". I agree with Dave here and presenting stoeckler data as refutation or Michael's " they are not much different " isn't persuasive. Yes what Michael says about two bath developers being able to produce a desired contrast index by extending time in bath A is true and not a fix nor inherent feature of any particular two bath BUT when all things are equal - times temperature agitation regime etc d23 is contrastier than thornton's which in turn is contrastier than stoeckler. why, because the level of imbibed metol in the film present for the B bath to do the rest of the development make a significant difference at the enlarger. I have seen this difference an have adjusted A baths according to the different films I use.

  2. #102
    Rudeofus's Avatar
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    El wacho, if BTTB as used by David Allen gives normal contrast and a straight curve, I wonder why he claims he got such different results compared to other developers.
    Trying to be the best of whatever I am, even if what I am is no good.

  3. #103

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    Dave Allen answers some of your question at post 91. I suspect though that his assertion is not sensitometric in nature and that you have understood his assertions as purely sesitometric in nature. I suspect that his satisfaction with thornton's two bath, like my own, lies in the impression of improved local contrast that thornton's two bath has over, say d76 1:1. i'm not certain that a stouffer wedge could furnish data in the area of local contrast. yes. two developers can achieve the same contrast index but yield qualities on print that are beyond the scope of sensitometry. perhaps tanning and staining vs mq developers is a good example of this.

  4. #104

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    Quote Originally Posted by el wacho View Post
    my statement still stands. ALL THINGS BEING EQUAL the extra 1.5 gr of metol in thorton's does yield a negative of greater contrast. that is why Thornton modified the Stoeckler two bath. Rudeofus is right in saying that Stoekler is a low contrast developer. Dave Allen is right for asserting that Thornton's two bath is "is no more a low contrast developer than many others". I agree with Dave here and presenting stoeckler data as refutation or Michael's " they are not much different " isn't persuasive. Yes what Michael says about two bath developers being able to produce a desired contrast index by extending time in bath A is true and not a fix nor inherent feature of any particular two bath BUT when all things are equal - times temperature agitation regime etc d23 is contrastier than thornton's which in turn is contrastier than stoeckler. why, because the level of imbibed metol in the film present for the B bath to do the rest of the development make a significant difference at the enlarger. I have seen this difference an have adjusted A baths according to the different films I use.
    Well, no, the extra 1.5g Metol in bath A does not necessarily increase contrast for a given development time vs Stoeckler. The amount of sulfite in Thornton (similar to Dalzell) is lower than Stoeckler, and the pH of bath A must be considered.

    Even if Stoeckler was a lower contrast developer than BTTB, one could rectify that by simply extending the Stoeckler bath A development time. It seems to me it is easier to change the development time to adjust contrast than it is to reformulate the developer. And contrast is primarily determined by development time in bath A. Again, development occurs in both baths.

    In any case, the statements el wacho makes are analagous to saying at a fixed development time of say 12 minutes developer X is more contrasty than developer Y. While that might be true for a fixed development time, it says nothing about whether developer X is more or less contrasty than developer Y. Developer X might simply be more active and require a shorter development time to give the same sensitometric results as developer Y.

    The point was to illustrate to MrBrowning (OP) how Metol-sulfite + alkali developers work relative to single baths, what the most effective controls are and how to alter contrast. You can do this with Adams's formula, Stoeckler, Leitz, Dalzell, Thornton etc.

    This is going in circles and off the rails so I'll just leave it at that. Best of luck.
    Last edited by Michael R 1974; 06-26-2014 at 09:23 AM. Click to view previous post history.

  5. #105

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    Quote Originally Posted by Rudeofus View Post
    El wacho, if BTTB as used by David Allen gives normal contrast and a straight curve, I wonder why he claims he got such different results compared to other developers.
    It is possible it could have to do with image structure characteristics (primarily less solvent action, and perhaps enhanced edge effects).

  6. #106

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    I've tested the difference that 1.5g of metol makes. i'm not speculating nor am I saying it necessarily does. I am saying it does because I've tested it. if I remember correctly, PE suggested that 'reformulating' ( what I would call adding a little more metol to) the developer according to the gelatin's absorbing capacity was a better approach. I intuitively arrived at that conclusion and was pleased to see PE say something in a similar vein.
    Nothing personal Michael but I haven't seen any of your data contradict my testing, in particular to the issue of metol levels in bath A and its irrelevancy to contrast. i'll most definitely be continuing with the evidence I have produced in my darkroom. I invite any one to mix two A baths (a stoeckler and a thornton) and two 12g sod metaborate B bath and see for themselves.

    "it says nothing about whether developer X is more or less contrasty than developer Y"
    never asserted it and it has never been my concern. I made a basic assertion - more metol more contrast, all things being equal.

    perhaps MrBrowning just unknowingly placed the highlights too high on the film and beyond the reach of any developer to retain tonal separation.
    Michael is right for attempting to disperse any myths regarding two bath development but the op's original question was the real matter at hand.
    Last edited by el wacho; 06-26-2014 at 09:04 AM. Click to view previous post history. Reason: intensity complexity and unity

  7. #107

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    I want to say thanks to everyone for there comments. I have learned a lot and still have a lot of questions but the biggest thing I have realized is I need to do more testing.
    Testing in regards to what Michael says and what Thornton said so I can have a better understanding of both. Plus it would be fun.

    el wacho,
    I may have very well placed the highlights to high. I metered strictly for the subject without thought to highlights (since at the time they didn't seem as important as capturing the moment).
    "The key to immortality is first living a life worth remembering." - Bruce Lee

    "It is better to travel well than to arrive." - Buddha

  8. #108
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    Quote Originally Posted by el wacho View Post
    Dave Allen answers some of your question at post 91. I suspect though that his assertion is not sensitometric in nature and that you have understood his assertions as purely sesitometric in nature.
    I just reread posting #91 and it says nothing about micro contrast or sharpness, and everything about the fact that he can get printable negs even if different frames on a roll are exposed under very different lighting conditions. I would interpret this as "gives me more latitude with normal development in high contrast scenes", i.e. a property well described by H&D curves.
    Trying to be the best of whatever I am, even if what I am is no good.

  9. #109
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    El wacho, if BTTB as used by David Allen gives normal contrast and a straight curve, I wonder why he claims he got such different results compared to other developers.
    BTTB gives the contrast that I want. Whether this is normal is another matter. As for it producing a straight curve - don't ask me.

    The reasons that I got results with BTTB that pleased me more than the other developers is simply I got the results that I wanted straight away with BTTB and I didn't with the other developers.

    At the core of developer choice is getting the results that suit one's work - as I explained in post#91

    For me the key things that I want from a developer are:
    • Relatively low levels of grain (given that I am using 6 x 7 film printed onto 16" x 12' paper)
    • Good level of apparent sharpness
    • Reasonable levels of acutance (impossible to define/explain but I know what I want)
    • Good tonal structure (again impossible to define/explain but I know what I want)
    • Being sure that I can place the dark shadows (where I want to retain detail) exactly where I want them secure in the knowledge that the developer will control the highlights (i.e. will not cause me to have very dense highlights that are hard to print or are virtually impossible to print).
    • That the developer can cope with the variety of scenes and subject brightness ranges that exist on a single roll of film.

    Bests,

    David
    www.dsallen.de

  10. #110
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    Quote Originally Posted by Rudeofus View Post
    I just reread posting #91 and it says nothing about micro contrast or sharpness, and everything about the fact that he can get printable negs even if different frames on a roll are exposed under very different lighting conditions. I would interpret this as "gives me more latitude with normal development in high contrast scenes", i.e. a property well described by H&D curves.
    Micro-contrast and sharpness were discussed in post #75 when commenting on the image that I included with this post.

    I believe that, over the course of this thread, I have explained a wide range of issues related to BTTB and why I like using it. Of course, I could have done everything in one enormous post but I don't have the time write such a long text and suspect fellow APUG members wouldn't have the time to read it!

    Bests,

    David.
    www.dsallen.de

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