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

Rudeofus

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You do realize that it is mostly the density in green and blue light you should be looking for. Red light (or the lack thereof) won't change your prints one jota ...
 

Alan Johnson

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The attached pics show a high contrast scene taken on TMY-2 1/125 f11 yellow filter developed in Catechol brew for 20m 68F.
The straight scan gives an idea of the low contrast which would need some holding back of the sun to print on silver gelatin paper.
My electronic "print" (for which apologies but it illustrates the point) shows that reflections of the sun on water but still keeping shadow detail can be photographed using this type of developer.
 

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Another experimental result attached, a variation on the formula which used ascorbic acid as the superadditive agent.

The latest test formula contains half the ascorbic acid, with development time extended from 10:00 to 12:00. The goal was even lower overall contrast than the first ascorbic acid formula, but with higher speed and a slightly straighter lower portion of the curve (ie like the initial Dimezone-Pyrogallol test formula). The formula is:

20.0g sodium sulfite (anhydrous)
0.5g ascorbic acid
1.0g Dimezone-S
----
1.0L

The result was extreme low contrast and very high film speed, still with a fog level the same as XTOL and ID-11 (developed to a normal gradient). Curves for XTOL and ID-11 are included.

Note since the orange tint at high exposure levels appears to exist with TMX100 regardless of developer, the attached plot shows all curves read through blue filtration. Since the readings through green filtration are very close to the white light readings, contrast with VC paper would be even lower - ie: super-extreme low contrast and flat highlights. I will put the blue/white curves in a separate post.

The basic idea has been to see how far this premise (ie N-infinity with no speed loss) could be taken. Even under extreme contrast conditions, I would find this to be too much compression. Of course other films will behave differently and I'm especially curious to see what can be done with TMY-2 for example. TMX100 is particularly easy to work with because it naturally has a gradual shoulder. With other films the formulas will no doubt require alterations, and these are still just "play" developers at this early stage. I'm hoping to do some test printing this weekend and see what the image structure actually looks like. I'm hoping additional tweaks could also allow for more sulfite.
 

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Shawn Dougherty

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Fantastic work, Michael. I'm moving next weekend and camping in the everglades the following week so I have decided to hold off on experimenting with the Pyro/Dimezone brew. It appears there is great merit to this form of N- development and I look forward to working with some of your formulas later this spring.

I'm also looking forward to your thoughts on image structure and such!
 
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Yeah I wouldn't burn any film on these formulas just yet. One thing that pleased me with this particular version is I was able to "straighten" the curve a little, which at first (based on the first set of formulas) I thought might be unique to the Pyro version. It would of course be nice not to have to use Pyro so this latest formula is encouraging. What it shows is there are so many possibilities here. I'd still like to also mix up some "XR-1" and H&W for comparisons.

I'm hoping Rudi, Alan and Gerald will have a look at these latest results and comment. Maybe at some point we could try to get some feedback from PE as well.

It also occurred to me, since this latest version resulted in even higher than normal film speed while keeping contrast exceedingly low, perhaps there could be some use for this type of thing as a push formula - you know - for the people always trying to shoot Tri-X at 3200. If fog can be kept in check, it could be something worth exploring for fun.
 

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I love doing night shots with Delta 3200 processed in POTA and Delagi 8. With low contrast developers you can compensate for Schwarzschild effect and excessive night contrast, and create very realistically looking images with beautiful highlights (light sources in the image frame), crisp mid tones (sections illuminated by these light sources) and still somewhat detailed dark areas. But even with the high night time contrast I frequently see myself enlarging the resulting negs with grade 4 to 4.5.

To my great joy I see Michael's latest graph for 1 g/l Dimezone-S and 0.5 g/l Ascorbic Acid with noticeably higher, but still very controlled, contrast than POTA/Delagi 8, and the toe end of the curve would reveal a great deal more shadow detail, too. So I'm very excited about this latest dev and will probably have to spend a couple of rolls of Delta 3200 on this.

There are a few things I would like to find out in the process:
  • POTA has extremely short working solution life, which makes it quite inconvenient for use. My hopes are that Ascorbic Acid not only straightens out the curve and increases speed, but also extends working solution life at least for a whole evening.
  • In Europe prices for Phenidone are so far below those of Dimezone-S, that it is a very tempting alternative, especially in a developer that uses a lot of it. From what I have read in the past, 0.75 g/l Phenidone should be similar to 1 g/l Dimezone-S.
  • Ascorbic Acid, while environmentally friendly and very easy to obtain, introduces its own set of problems, see "sudden death of Xtol". We know that Sulfite and tap water both bring in Iron ions which catalyze the decomposition of Ascorbic Acid. There are two known compounds which avoid Iron ion catalyzed decomposition of Ascorbic Acid in photographic developers: Dequest 2010 and DTPA.

Dequest 2010 is very acidic (pKa1 = 1.7, pKa2 = 2.47) but can be neutralized with NaOH and should have little effect on buffering. It is listed as pharmaceutical compound in the US and could be difficult to obtain by non-commercial entities. DTPA may be easier to get, is used successfully in Xtol, but its pKa values are spread all over the place: pKa1 = 2.3, pKa2 = 2.6, pKa3 = 4.17, pKa4 = 8.26, pKa5 = 9.48. This means it will likely affect buffer behavior and therefore sharpness and other properties of that dev.
 
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Good questions, Rudi.

I've been using distilled water, but you are quite right Iron can be introduced by the other ingredients. Thus far I have not had this fail on me, but it is definitely something worth thinking about. On thought I had: when I mixed the "baseline" formula (just 20g/L sulfite and 1g/L Dimezone-S), as expected it went orange during mixing, like POTA does. However all the test formulas which included the "regenerating" superadditive agent (including the latest formula with only 0.5g/L ascorbic acid) mix colourless. So I was thinking, in the case of the ascorbic acid formulas, if Fenton were to show up and destroy the ascorbic acid, I'd expect the solution to go orange. Does this make sense? If so, it would at least be a visible sign of developer death. A way around this entirely would be to go with HQ and adjust the formula. I'm quite certain based on the initial results that can be done. The wild card is image structure. I haven't done any testing on that yet, although I'm hoping to print some tests this weekend.

Regarding Phenidone vs Dimezone-S, my understanding is that if the weights are adjusted, Phenidone and the various available methylated derivatives including Dimezone-S should be expected to have the same photographic characteristics. I don't know if this is correct or not, however. If I had had Phenidone I would have used it. But I happened to have some fresh Dimezone-S so I started these experiments with it and figured I'd continue until it runs out. All this to say there was no special reason for me choosing it over Phenidone.

One thing I'm thinking about is if it would be possibly to replicate the sensitometric results, but with finer grain (assuming it is not fine already, which we don't know) by adjusting the concentrations of the developing agents while increasing the sulfite concentration to say 50g/L for example.

A couple of questions:

1. How do you know when your anhydrous sulfite has crystalized to its hydrated form?
2. While I've experimented briefly with the original Levy POTA formula, I've never tried Delagi's version. What differences do you notice? The only references I have are in Anchell/Troop. My understanding is Delagi modified POTA because he thought it had crap sharpness, but other scientists have said the original POTA is sharper than any of the variants based on it.
 

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Michael R 1974 said:
I was thinking, in the case of the ascorbic acid formulas, if Fenton were to show up and destroy the ascorbic acid, I'd expect the solution to go orange.
Click to expand...
I don't think so Michael, it seemed to me that the ascorbate oxidation products are only orange in absence of sulphite, at least to start with.
(there was a url link here which no longer exists)
 

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It requires tiny amounts of oxidized Phenidone to create a distinct pale orange color. Put a small amount of Phenidone in a film tank and add tap water, and it will be orange. Pour it out completely and refill the film tank with tap water, and it's orange again. You can do this a few times before the orange cast finally disappears. So yes, oxidized Phenidone is very visible.

Xtol contains Dimezone-S and a secondary dev, but nobody ever saw this orange hue when Xtol went bad. Somehow I have the impression that it requires trace amounts of remaining Ascorbic Acid to prevent the Phenidone orange cast even if the dev has deteriorated substantially by then. We also know that Ascorbic Acid lowers pH if oxidized, which brings in a second factor for lowered developer activity. Because of your low levels of Ascorbic Acid in your dev this may not influence your developer as much as it impacts Xtol.

Looking at and comparing your graphs for 20 g/l Sulfite, 1 g/l Phenidone and 0, 0.5 and 1 g/l Ascorbic Acid, it may be too late even if that orange cast finally appears. There is a profound change in characteristic curve and developer speed between these three, so for the sake of consistency we should either take measures to protect the Ascorbic Acid, or use the dev right after mixing.

Michael R 1974 said:
1. How do you know when your anhydrous sulfite has crystalized to its hydrated form?
Click to expand...
Mix it 1:1 with Sodium Metabisulfite and measure pH. The difference in molar weight between anhydride and monohydrate is >10% so it should give a measurable difference. You did get a pH meter, yes?

Comparing POTA and Delagi 8 recipes yields two differences:
  • Delagi 8 uses a small amount of Borax to improve buffering. We know from my measurements posted early in this thread that POTA is more or less unbuffered, that extra bit of Borax should keep pH in the same ballpark but with some extra buffer strength. I would expect reduced sharpness from higher buffer strength.
  • Delagi 8 uses restrainer, which could have impacted sharpness like the KI did in Crawley's FX-1, but that is said to no longer work with modern film stock anyway. Since Delagi 8 is not the most popular developer around, that notion of improved sharpness may be outdated. My Delta 3200/Delagi 8 enlargements look sharp, but so does any other 4-6x enlargement of this film. I'm afraid the long exposure times combined with the fragile tripod I use for my night shots may prevent meaningful analysis of sharpness from my samples.
 
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Thanks Rudi and Alan for your thoughts on this.

Alan, the colour change I was thinking about was the oxidizing Phenidone, not the ascorbic acid. Even in the presence of sulfite, Phenidone on its own in solution begins oxidizing pretty much immediately, which is why POTA (or my plain Dimezone/sulfite formula) goes orange during mixing and needs to be used right away. However once you add a small amount of secondary regenerating agent such as ascorbic acid, Pyrogallol or HQ, the orange colour goes away because the Phenidone is somewhat "stabilized". So, in a colourless aqueous solution of sulfite, Phenidone and ascorbic acid, my line of reasoning was that since the presence of ascorbic acid keeps the solution colourless, if the ascorbic acid was then destroyed by the Fenton reaction, the Phenidone would again go orange. However Rudi has pointed out the flaw in my logic here, as it appears only a tiny amount of ascorbic acid is required to keep the solution colourless. Most of the ascorbic acid could potentially be destroyed and you might not see a colour change - which indeed seems to be why people never saw their dead XTOL change colour.

Incidentally, I haven't noticed a straw colour, even after about 30 minutes of mixing. The test developers have all looked pretty much colourless so far.

Rudi - I'm down to a few pH meter models and trying to decide on one. It is clear I need one, but I'm still nervous about using one and not really knowing how to work it or maintain it properly. I'll get there, though.
 

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must buy some ascorbic acid tomorrow...
 
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Here are some curves for TMY2 with the same test formula, and XTOL. Regarding the kink in the TMY2 curve, we've seen this before and tested it with various developers (see Mark Overton's thread) and it appears to be normal.

Fog was 1 density unit (0.01D) higher than XTOL, but this is within the margin of error so we can't say much about it. This is ridiculously low contrast and very high film speed (although the film's inherently higher highlight contrast handles it better vs TMX's long shoulder which can become excessively flat), but again, the idea here was to see how far this can go (I wonder if the Pyro version might produce an even straighter line). For actual use perhaps less Dimezone and a 1:1 ratio with ascorbic acid. Etc. (ie a less extreme formulation).

I'm thinking maybe trying this with a film like Acros which normally has very high highlight contrast.

Anyhow, more food for thought.
 

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Shawn Dougherty

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Sweet! I would most likely be using this with HP5 or TMY2 (though I'm trying to stay all Ilford...) so this is of particular interest.

Was the XTOL developed to a pretty hearty N- like the last time?

Thanks again, Michael.
 
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Hi Shawn, no the XTOL curve you see in post #89 is "normal" development. The idea was to illustrate that even when developed to normal contrast, the "speed" given by XTOL (an excellent reference developer for full film speed), is lower than that of the test formula developed to minus-infinity. I also wanted a good normal reference point for TMY2 graininess so I went with normal development in XTOL. However I also developed some TMY-2 with minus development in XTOL last night (along with Delta 100 and FP4) so I could do some further comparisons for speed and grain. I'll plot the curves and post them.

Thanks for the continuing feedback. This has been fun so far. I figure while I'm at it I'll mix up some test formula and store it in a full glass container for a day or so to see if can survive at all or if it is truly a mix-and-go like POTA.
 

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Michael R 1974 said:
I figure while I'm at it I'll mix up some test formula and store it in a full glass container for a day or so to see if can survive at all or if it is truly a mix-and-go like POTA.
Click to expand...

From what I have read about Ascorbic Acid so far, it deteriorates within hours if you don't have a sequestering agent for Iron ions in your solution. If you look at Ryuji Suzuki's DS-12 formula, he uses 0.2 g/l Dead Link Removed for this purpose. You'll love Salicylic Acid because it is fairly easy to get for us amateurs and with its low pKa it does not affect buffering of your developer.
 
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Rudi - are the Iron ions basically assumed to be there because of impurities in all photo-grade compounds, and also because there are still some left in distilled/deionized water? I guess in essence what I'm asking is - do we know with certainty the ascorbic acid will be destroyed, or is the sequestering agent added to eliminate the risk?

Just to follow up on my previous note to Shawn, attached is the same TMY graph as before but with a "minus" XTOL curve added.
 

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Rudeofus

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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. Look at this document for experimental numbers.
 

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Michael R 1974 said:
Just to follow up on my previous note to Shawn, attached is the same TMY graph as before but with a "minus" XTOL curve added.
Click to expand...

Wow, that toe looks ever better compared to the N- XTOL curve!

I was thinking of this over the weekend while I was exposing some film indoors to a high contrast scene. It was my last roll of Kodak 125px so no point in testing and I put the shadows way up on Z5 for N- developing like I normally do... it sure is going to be nice to use film at full speed in these situations.
 
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Rudi - going back to acid-base chem for a moment, suppose we increased the sulfite concentration from 20g/l to say 40-50g/l. We know based on your pH tests this should not result in a significant pH increase, however would the higher concentration of sulfite buffer more against the pH drop from the addition of ascorbic acid? I know we've already established the buffering strength of sulfite is low, but just wondering if it would increase measurably at the higher concentration.
 

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Sulfite is a terrible buffer at pH 9.5 and at the same time an excellent buffer around pH 7. Doubling the amount of Sulfite will make it half as terrible a buffer at pH 9.5, which is still terrible. You will not get half the pH drop with a given amount of Ascorbic Acid, but you will get the same pH drop with twice the Ascorbic Acid, if that makes sense.

If you want to improve buffering, you will first have to know at which pH you want to buffer. If you want to maintain pH between 9 and 10.5, a Carbonate/Bicarbonate buffer will work wonders, whereas Borax/Boric Acid works nicely between pH 8 and 9.

In my opinion the poor buffering of Sulfite is not an accident. Phenidone has often been claimed to give worse sharpness than Metol, so a poor buffer might work to POTA's, and also your dev's, advantage.
 
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Weak buffering is what I wanted so, mostly because all things being equal, poorly buffered solutions tend toward lower contrast. So if twice the sulfite is still a terrible buffer, that's good. Regarding sharpness, unfortunately no matter what there won't be a way for me to measure that objectively. I've done some high magnification prints to try to visually compare graininess at equal densities and exposure levels, but it is difficult.

Ultimately a pH of ~8.5 or lower is what I wanted.

Another possibility which crossed my mind as a backup plan for achieving slightly finer grain without an increase in buffering was to add some sodium chloride instead of increasing the sulfite. But I'd rather adjust the sulfite if I can instead of adding more ingredients.
 

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My theory in photography goes "if you can only measure a difference but not see it, then there is no difference".

Michael R 1974 said:
Ultimately a pH of ~8.5 or lower is what I wanted.
Click to expand...
D76 does that nicely with Borax.

You spent all this effort on creating a developer that gives you full speed, and then you'd throw all that away by adding Sodium Chloride? Unless this new dev is an absolute grain monster, I wonder why you would want to mess around with solvents. As far as I remember, Delagi 8 gave me nice and finely grained results ...
 
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Rudeofus said:
My theory in photography goes "if you can only measure a difference but not see it, then there is no difference".
Click to expand...

I suppose, but the problem is we sometimes see things which are not there.

Rudeofus said:
D76 does that nicely with Borax.
Click to expand...

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.


Just keeping the options open. I'm not talking about a huge amount of NaCl or additional sulfite, and NaCl is a fairly weak silver halide solvent and/or restrainer.

While a definition of speed is problematic with such a low contrast developer, if we simplistically use a fixed density point of say 0.1 above B+F, this latest version of the test developer is actually giving a speed increase vs just maintaining speed. So depending on what you want, there is actually some speed to spare, in a sense. This robust absolute threshold speed has to be weighed against image structure characteristics and tuning may be required to get the best "balance". The end game was to have something which gives a curve very similar to XTOL developed to low contrast (say N-3 in ZS terms), but shifted to the left so that a "normal" EI is maintained. 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).

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
 
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