Also keep in mind the time your film spends in the A solution. I've used TD 201 as well as Thornton and several other D-23 variants and have found the times recommended for the A bath to be too short for me. I did two rolls of 400 - Arista Premium and HP5+ - at six minutes in the A bath with intermittent agitation. That's the time that works for me; as they say, your results may vary.
"The amount of solvent action in developers depends on much more than the concentration of sulfite."
interesting but how does it exactly bear upon the topic? the op wants to know if 75gr is going to improve sharpness over 100gr. in a developer consisting of water, sodium sulfite and metol i'm struggling to see where else the solvent action is going to come from esp. when it is the classic parameter to modify when one wants solvent action and the lack of grain associated with it.
Solvent action comes from the sulfite, but the amount of time the sulfite has to act can be as important as the concentration. Assume for a moment there was no part B in OP's developer. Reducing the amount of sulfite also reduces the pH, which, all things being equal, increases development time. This gives the sulfite more time to etch the grains. So even though you have less sulfite, the difference in graininess might be very small or even immaterial. This is the principle used in the formulation of D-25. It is D-23 with a lower pH, therefore longer development times, and more solvent action from the same concentration of sulfite.
Now add the B bath to the equation. Development is rapid in the B bath, which means the sulfite in the absorbed developer has less time to act than if full development had been carried out in bath A. This should make the difference in graininess between having 100g/L or 75g/L in bath A even smaller.
This is one of the reasons I initially asked OP how he knows TD-201 isn't sharp.
Two additional concerns: 1) A sulfite concentration of 80g/L is said to give maximum solvent effect. 2) "Sharpness" is a very complex thing and does not necessarily increase with decreased solvent activity. But that's a whole other topic.
That's correct: in a metol-only developer, sulfite acts as solvent AND as activator (pH).
Originally Posted by Michael R 1974
But in a two-bath developer like TD-201, temperature or time has little or no effect, at least within the 20-22°C range. That's a difference between two-bath developers and D-23 vs. D-25 and that's why I asked how to increase activity chemically.
I wonder how to improve sharpness, I did'nt say it's an unsharp developer.
Originally Posted by Michael R 1974
Understood. So I'd go back to my earlier post. As you know, TD 201 and most of these two-baths are based on some development in a solvent A bath followed by an alkali B bath to exhaust absorbed developer from the A bath. To get less solvent effect, increase the activity of either bath A or bath B, or both. Increasing the activity of bath A also raises contrast. Alternatively you could go to a low-sulfite, true divided developer where there is little to no development in bath A. The danger there is excessively low contrast, and it can sometimes be difficult to achieve uniformity.
Another thing you could try is decreasing both the Metol and sulfite in bath A with different times. I'm suggesting this because the Metol salt itself is acidic.
Perhaps the easiest thing to start with would be to simply reduce the sulfite to say 50g/L in bath A, and extend the time in bath A (or add some alkali). Perhaps this will have enough of an effect. Difficult to say. There are many variables here. And it also goes without saying you'd have to evaluate things like film speed as you go.
avoid the run around ( as i have done ). you should only rely on your empirical results. i have compared the two same frames ( shot the same frame 12 times in 120) and compared 100gr to 80gr ( also compared 80 to 65gr ) and used a 35gr sod carbonate/L B bath. all things being equal there is an increase in perceived sharpness as the sod sulfite decreases. i did not notice a drop in activity as the sod. sulfite decreased and the metol stayed at 6.5gr. Harold33. it's one test and you'll develop your own knowledge on the subject matter. a picture really is worth a thousand words...
ps. to increase the 'two bath' effect you actually have to increase the level of metol (say, to around 6.5gr/L) because how much metol is absorbed into the gelatin depends on the metol concentrate in the A bath. B bath can only develop the metol that is in the gelatin. i have also looked at negatives developed in only A bath then compared to the same negative finished in B bath. B bath does an amazing amount of development. Thornton was right when he said that you only need to develop between 1/2 to 2/3 of the recommended time for A bath only development because B bath really does 'finish' off the negative. the more metol there is ( i have tested up to 10gr/L in 1gr intervals from 7gr ) and all things equal, the more there is an increase in development (A+B) BUT most importantly the 'two bath' effect is increased.
I have read that over and over that no development takes place in bath A and that time and temp do not matter with a 2 bath developer.
Originally Posted by Harold33
THIS IS NOT TRUE.
Maybe it is with some 2 bath developers but not with a MS two bath like this. I have done controlled tests.
I shoot a several whole rolls of 120 and cut them into strips, then tested in various versions of bath A alone and finished with bath B.
In all 2 bath developers I tried I got a lot of development in bath A alone.
The only developer where I really got almost no image in bath A alone was Diafine.
You need to run your own tests.
My favorite 2 bath I came up was a divided version of Xtol. It gave me perfect negatives for high key subjects with Plus-X.
With other films the results were good just not totally fantastic.
(Imagine a snow scene where you can see all of the detail in the snow that was actually there and also a dark spruce tree that was not just a dark spot in the photo)
Now sadly Plus-X is no more.
Brian is correct. With a "true" divided developer, no development takes place in bath A. The developing agent is absorbed. It is then activated and exhausted in bath B. Time/temp are less meaningful in that context although they can still potentially make a difference in how much developer is absorbed and whether or not development in bath B is truly to completion. TD-201, on the other hand, is not a true divided developer. Development takes place in bath A, and is then completed in bath B. Time and temperature and agitation matter.
while you decrease sulfite or increase metol - you decrease pH of bath A and result activity decreased. so you need keep pH while decreasing amount of sulfite. buy cheap pH meter, decrease amount of sulfite to 40-50g/l and add some alkali like sodium carbonate to keep pH
Originally Posted by Harold33