A very low contrast, low pH, full speed POTA variant

Rudeofus · Feb 26, 2014

Michael R 1974 said:
True, but it contains the acidic Metol salt. And to be honest I'm still not entirely clear on precisely how D-76 achieves its operating pH. Haist says there is just enough borax to neutralize the acidity of the Metol salt, and when I read "neutralize" I take it to literally mean the acidity of the Metol salt and the alkalinity of the Borax are gone. If that is the case you're left with the Metol free base, 100g sulfite and 5g HQ. I guess 5g HQ is enough to lower the pH of the sulfite solution all the way to 8.5? Another way to look at it would be to say the Metol salt and HQ bring down the pH of the sulfite solution, the the Borax then maintains the resulting pH (with some buffering). Confusing.

I think that the phrase "just enough to neutralize the acidic Borax" is a gross oversimplification of what happens in D-76. We know that Borax is not just some alkali, it is a good buffer at 8.5.

Michael R 1974 said:
We sort of got there with the 1:1 ratio of Dimezone/ascorbic acid. But before pursuing that further I first wanted to see how far I could push the idea of maximum speed/minimum gamma. As a proof of concept, we've exceeded expectations, but in reality I think from a tone reproduction perspective I would need to pull back a little on this. More contrast is needed (in my opinion).

There is a profound difference between your dev and Xtol: the latter one has to work with tap water which can have quite an effect on solution pH as I hear. It also has to work with all kinds of film, fresh and aged. Result: Xtol (and any other commercially sold developer) has to go easy on film or forums are full with "OMG Xtol gave me foggy results!!!" postings. With a home brew developer, optimized for your personal choice of film and development procedure, you have a lot more degrees of freedom that you can use (and apparently have used) to your advantage.

Michael R 1974 said:
So far in the initial prints from this extreme version, grain seems similar to that of XTOL 1+1 developed to normal contrast, but I'm not sure, and a lot more printing of various comparative densities, exposure levels, and then image evaluations need to be done. From my perspective this is still just an early-phase test of various concepts. Sorry if that's a little depressing

It sounds more depressing than it needs to. You have just created a developer that fills an important niche for you and some others here. That developer keeps contrast under control with a very straight characteristic curve and full speed. So what if it ends up a bit more grainy and a bit less sharp than Xtol? Xtol lost you a couple of stops if you developed to the same contrast for crying out loud! Can you improve your dev? Most certainly! But you can still enjoy the results you're getting right now. Once you start looking at your images after greater enlargement and see things you want improved, you can work on that dev step by step, raise Sulfite, lower Sulfite, add other solvents, try out different restrainers, maybe add a weak buffer, or a sequestering agent. None of this has to happen over night ...

Mr Bill · Feb 26, 2014

Rudeofus said:
Sodium Sulfite, photo grade or not, has been reported as major source of Iron ions, so I'm afraid you need to address Iron one way or another.

I believe the old ANSI photograde specs typically required that iron be at 0.001% or less. That is, iron could not be present in excess of 1 part in 100,000. So that if you mixed a developer like D-76, with 100 grams/liter sodium sulfite, the iron due to that should be less than 1 milligram per liter. (I'm guessing that ISO still uses the same limits.)

I don't know what amount of iron will cause problems for you. I had experience with C-41 iron problems, where, as I recall, we saw a slight, but definite shift in control charts with city water running at 5 or 6 mg/l (my fuzzy recollection). (It was a temporary issue with water treatment, ferrous sulfate (or similar) was used as a floculant to treat turbid river water.)

Xmas · Feb 26, 2014

Rudeofus said:
None of this has to happen over night ...

Forget about Michael's perception problems I'm calling it 'R1974i', maybe I might add restrainer or sequester or buffer but if it works with my deionised water that would be an option. The i is in case I need to change to Michael's next soup. I need to keep records...

I've bought the ascorbic acid...

I will report any interesting results - it is normal I underexposure and burn on highlights on the same film so it is a good test.

Shawn Dougherty · Feb 26, 2014

For what it's worth I'm planning on using distilled water and mixing on demand. Given the simplicity of the formula and the specialized nature of the extreme N minus development, I find that to be an attribute. No point in having something sitting around that I won't be using all the time.

removed account8 · Feb 26, 2014

Rudi - I hear you. Don't get me wrong I think this is a good start and I haven't given up. All I'm saying is formulating a developer is more than just throwing some nearly arbitrary amounts of compounds together and generating some curve data. I know you know this already of course, but I'm a stickler for quality, and a hardass for evidence. When a formula comes out of Kodak or Ilford, we know it has been carefully evaluated not only with sensitometry but also image structure. On the other hand, for so many of the home brews people have adopted over the years, we have virtually zero data or supporting evidence of any kind to support the claims made. I guess I'm just hypercritical, but if this thread had been started by someone else, I'd be challenging him/her on all these things.

I still feel almost "silly" trying to come up with my own formula for any other reason than to learn some more, no matter how much I've studied the books by Haist, etc. Remember Mark Overton's thread when he was working on his XTOL clone concentrate? The chemistry going on in that discussion with PE etc. was mostly way over my head.

removed account8 · Feb 26, 2014

Shawn Dougherty said:
For what it's worth I'm planning on using distilled water and mixing on demand. Given the simplicity of the formula and the specialized nature of the extreme N minus development, I find that to be an attribute. No point in having something sitting around that I won't be using all the time.

This is the premise I started out with - ie a one-shot formula mixed and used. The prospect of storage/shelf life introduces a whole extra level of complexity.

Rudeofus · Feb 26, 2014

Mr Bill said:
I don't know what amount of iron will cause problems for you. I had experience with C-41 iron problems, where, as I recall, we saw a slight, but definite shift in control charts with city water running at 5 or 6 mg/l (my fuzzy recollection). (It was a temporary issue with water treatment, ferrous sulfate (or similar) was used as a floculant to treat turbid river water.)

The difference between C41 and Ascorbate developers is that, unlike CD-4, Ascorbate suffers from catalytic decomposition in the presence of Iron (see Fenton reaction). The Iron ions are not used up in the process and continue doing their evil work until all Ascorbate is gone. As the paper I linked to shows, this decomposition happens within hours, not months, unless you add a powerful sequestering agent. I already provided three capable options here in this thread, Ryuji Suzuki did some further research into this topic.

Mr Bill · Feb 26, 2014

Rudeofus said:
The difference between C41 and Ascorbate developers is that, unlike CD-4, Ascorbate suffers from catalytic decomposition in the presence of Iron (see Fenton reaction).

I understand, I was mainly explaining how I happen to know something about the iron content of certain waters. And an idea of how much might be found in photograde chemicals (based on actual ANSI standards).

I don't know anything about the ascorbate developers (and no plans to be changing that).

Alan Johnson · Feb 26, 2014

I can see no reason why ,when taking actual photographs, the film should not be developed to a density approaching Dmax as doing this should give better highlight separation.
But it seems that it may not be possible to produce H&D curves corresponding to this case as it covers more exposure stops than possible with any step wedge.

Rudeofus · Feb 27, 2014

Alan Johnson said:
I can see no reason why ,when taking actual photographs, the film should not be developed to a density approaching Dmax as doing this should give better highlight separation.
But it seems that it may not be possible to produce H&D curves corresponding to this case as it covers more exposure stops than possible with any step wedge.

The enlarger lens will kill that effort. Anyone who rags about the importance of the D>2 region of a film is strongly encouraged to make a contact print of a Stouffer wedge and then do a similar sized enlargement of this wedge. The difference is quite enlightening ...

Alan Johnson · Feb 27, 2014

Maybe I did not put that very well, try again.
IMO it is preferable that eventually the optimum development time should be determined by taking some real photographs and making silver gelatin prints from them.
It may not be the 10min used in making the curves presented so far, some caution is needed in drawing conclusions from them.

Mr Bill · Feb 27, 2014

Alan Johnson said:
Maybe I did not put that very well, try again.
IMO it is preferable that eventually the optimum development time should be determined by taking some real photographs and making silver gelatin prints from them.
It may not be the 10min used in making the curves presented so far, some caution is needed in drawing conclusions from them.

Hi, I haven't been following this thread closely, but I think Michael intends this for special situations, to bring a very wide luminance range into a (conventional) printable condition.

I sort of doubt he'll be too happy with it for any sort of "normal" subject because of the way tones are reproduced. But I suspect he's also doing it for fun, just to investigate things. To me, "for fun" is always a valid reason that is hard to argue against.

removed account8 · Feb 27, 2014

Alan, I think we'd all agree exposure, and development time/contrast need to ultimately be determined by the individual user based on the subject, desired negative characteristics, printing style/controls, aesthetic preferences etc etc. But from an experimental perspective we have to start somewhere if we want to make meaningful comparisons, hence the curves based on constant/controlled exposure and processing conditions. It eliminates the obvious complicating variables involved in attempting to make objective comparisons based on pictures. So basically what I'm saying is you have "lab" testing and "field" testing, and they are both important when attempting to invent something (or whatever I'm actually doing here ). First you need data. Then you have to actually use the stuff and see if you like how it works for you. The goal here was to see if it is possible to get low contrast (for very high contrast subjects) while retaining both full film speed, and a long exposure scale (ie without destroying highlight detail). And then of course there is image structure to consider.

Will the resulting negative be acceptable from a tone reproduction perspective? It will depend on the situation, subject matter, printing controls and of course the individual's preferences.

Still not sure what that has to do with D-max though.

Alan Johnson · Jun 5, 2014

I tested the Catechol version (Posts 61, 77) for longevity and contrast.

After it had been stored in a full sealed glass bottle for nearly 4 months, TMY2 was developed in it for 28min 20C. I just chose this time to give what seems like a reasonable density. Although I exposed it at EI=200, exposing at full box speed would probably have been satisfactory.
It still works after ~ 4months (attachments).

It captures the dark foreground/sunlit clouds with unnecessarily low contrast,(flat attachment), although printable by masking the sky and printing it at higher contrast (enhanced attachment).
The low contrast seems more appropriate for reflections of the sun on water, and clouds very close to the direction of the sun (Post 77).
It is a very low contrast developer.

removed account8 · Jun 5, 2014

Just keep in mind none of the original formulas used Catechol so it is difficult to make comparisons. And most of the experimentation I've been doing has been with the Dimezone-Ascorbate combination. So far I have focused on the TMax films and Delta 100. TMY-2 seems to be the easiest to optimize this formula for, at least as far as curve shape goes. TMX is ok, but the formula needs tweaking. Delta 100 has been a challenge. I haven't found a ratio that has worked properly yet. I'd also like to make it work for FP4.

Another caution here is these were intended as mix-and-use, one-shot developers. So any kind of storage or shelf life was not part of the criteria.

Barry S · Jun 5, 2014

I've been testing some Kodak MIN-R EV mammography x-ray film I got cheaply. It's extremely contrasty (see the curve) and I'd love to find a low contrast developer so I can use it for pictorial use.

removed account8 · Jun 5, 2014

I haven't tested any of these experimental formulas with high contrast/doc films yet, but they may be of some use. I'm hoping to do some more work on all this but I have been busy with other things over the past several weeks.

A very low contrast, low pH, full speed POTA variant

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