Michael R.'s curves show that BTTB is a low contrast developer with a more or less straight characteristic curve (yes, I was surprised by that, too). What I don't understand is why David Allen wasn't able to adjust his contrast by choosing different paper gradations. I've done some tests with Foma 312 paper and a 4x5" Stouffer wedge, and the differences in dynamic range with different gradations are surprisingly high.
Michael R.'s curves show that BTTB is a low contrast developer with a more or less straight characteristic curve (yes, I was surprised by that, too).
Sorry, I do not think so.Michael R.'s curves show that BTTB is a low contrast developer with a more or less straight characteristic curve (yes, I was surprised by that, too).
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.
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.
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.
For me the key things that I want from a developer are:
Bests,
- 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.
David
www.dsallen.de
Dave answered the OPs question about n-1...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.
Do you meant Foma instead of Forma?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?