Why not 2 baths developer only?

[john_s]

I think you'll find that it's not that at all if you test it. The ratio of the agents is different, the amount of sulfite is different, and the buffer setup is different. So, no, not just divided D-76. Having used quite a lot of divided D-76 (both Haist and Vestal varieties), I can also attest that it works quite differently. Being speed-neutral or speed-boosting (2B-1) vs speed-losing (divided D-76) not being the only major difference. Paul changed the amount and ratio of the developing agents which moves it closer to the ratio that a theoretical D-76 would have if we were to accept that some amount of phenidone substituted for some amount of metol would produce identical results if the superadditive relationship remained the same. That does not make it divided D-76.

I think Lachlan considers many developers to be D76 derivatives. In a post last year he states that Pyrocat is a D76 derivative too.

ID-11 alternative?

That's an awesome resource, thank you! I'll be able to get to it when you provide the recipe to combat laziness 🙃 No, seriously, it does make it seem doable to my non-chemist brain. If you can make a cake, you can also scratch-mix a developer. Actually, it's even simpler and more fool proof...

www.photrio.com

 

[Sidd]

! PC-512 looks interesting. I'm going to read that thread. I'm sure I'll have a question about it soon.

Definitely try PC-512, it's a wonderful developer. Presently I am mostly using it as my go to developer.

 

[Lachlan Young]

many developers to be D76 derivatives.

It's about the developing agent relationships. The buffering and target pH were being played around with by Kodak etc from day 1.

PQ offers some potential inherent benefits for film development that MQ doesn't. Most of the purported effects of the staining developers come from the effects of either high dilution metol-only developers or the effects of a PQ type (Catechol being an isomer of HQ) at particular pH's. This has been seemingly well known in the industry for a long time (and the couplers produced by the agents used to produce 'stain' were well investigated too), but never percolated out to the popular press, who instead seem to have preferred to persistently publish questionable re-inventions of the wheel.

 

[relistan]

It's about the developing agent relationships. The buffering and target pH were being played around with by Kodak etc from day 1.

This is true, but that does not imply that the rest of the developer does not matter. It also does not imply that changing the ratios does not have desirable effects. Likewise, the right ratio with the wrong pH and buffer and other balancing produces bad outcomes. If everything were settled there would not be such a wide variety of developers that produce different results.

PQ offers some potential inherent benefits for film development that MQ doesn't. Most of the purported effects of the staining developers come from the effects of either high dilution metol-only developers or the effects of a PQ type (Catechol being an isomer of HQ) at particular pH's.

Yes, I agree with that.

This has been seemingly well known in the industry for a long time (and the couplers produced by the agents used to produce 'stain' were well investigated too), but never percolated out to the popular press, who instead seem to have preferred to persistently publish questionable re-inventions of the wheel.

It’s not reinventing the wheel. That’s the part where you and I will probably always differ.

 

[Sidd]

This is true, but that does not imply that the rest of the developer does not matter. It also does not imply that changing the ratios does not have desirable effects. Likewise, the right ratio with the wrong pH and buffer and other balancing produces bad outcomes. If everything were settled there would not be such a wide variety of developers that produce different results.


Yes, I agree with that.

It’s not reinventing the wheel. That’s the part where you and I will probably always differ.

What you people must carry on, is that, people like you have to carry on with experiments. Otherwise, this fantastic tradition of black and white film development will be a lost and dead chapter in history. Archeologists will have to some day dig on the subject. There will be no Kodak lab, no BJP and others. I myself would like to contribute also, but, don't have the required knowledge of chemistry nor decades long experience.

 

[Alan Johnson]

The optimal starting point ratios for PQ/ MQ etc have long been published in the standard reference works (see Levenson in the SPSE manual for example), and it seems that an awful lot of the time all that people are doing is inadvertently demonstrating that Kodak et al did the work correctly the first time round.




My own understanding of what people seem to think 'compensation' means is less dense highlights without screwing up midtone gradients via lower average gradient aim. This is essentially what the DIR couplers in XP2 are specificially aimed to deliver, rather than a much longer linear curve at a lower gradient. That people who are messing around with developers often end up doing the latter instead is, I think, the main source of the confusion.



Yes and no. Development inhibition effects potentially allow for better highlight control, finer granularity and better sharpness. Developer formulation is part of the story, but emulsion structure is arguably even more important. It is a pretty complex and (still) rather commercially sensitive area.

Solvency can allow access to (e.g.) iodide placed in the emulsion such that it will produce inhibition effects where it is released; highly dilute metol only (less than 0.5g/l working solution) can produce desirable effects via exhaustion, but not when a source of semiquinone is added; Phenidone and PQ (etc) developers can deliver inhibition effects without needing very dilute single-shot solutions, and the effects can be altered via the P:Q ratio. Adding 1-Phenyl-5-Mercaptotetrazole (PMT) restrainer can produce useful effects allowing a non solvent PQ developer to still produce fine but sharp granularity (and excellent highlight density control, with the added benefit of massive safety margins for those whose process control is poor or more-talked-about-than-enacted). Some of this has been commercialised by Kodak, Ilford etc in the last 30-40 years (and they've outflanked in research many much-talked-up formulae, subjecting them not just to a battery of properly tough tests of sharpness, granularity etc, but also double blind print comparison tests across wide-ranging enlargement sizes).

Thanks to Lachlan for this explanation.
Re phenidone inhibition effects, does this mean that phenidone/dimezone s is not only adsorbed on the grains but prevents the development of neighbouring grains? Is this similar to the effect when ascorbate is oxidized via the strong dehydroascorbic acid?