Anybody using WD2H+?

[Alan9940]

After many years of using a few different pyro developers, I've caught the itch to try WD2H. I found an old LFPF thread where John posted the correct formula and showed that he used 25ml A + 25ml B + 1600ml water to tray develop FP4+. Working out the dilution ratio here it's: 1+1+64. That's a somewhat odd dilution to my mind and he may have done this to extend development time. Is anybody else using this ratio or do you stick to the normal 1+1+50 of standard WD2D+?

Thanks for the help.

[Mark J]

I did Alan, I mixed some up early this year and tried using it. I agree that the dilution seems to be 1+1+64.
( ps. i still don't believe there is such a thing as WD2H+ , I think it's WD2H. It's confused by there being WD2D+ before it )
...Anyway, then the story gets messy. I got a very thin couple of negs from the first mix. I talked to John Wimberley ( we were corresponding already re. the Durst 138S ) for de-bugging ideas and then got a pH meter and tested the B solution, then the full developer mix, both were too low, not alkaline enough.
I concluded that there was either an error in the sodium carbonate that I'd been sold, or I had mixed the wrong dilution somehow.
I then bought some more carbonate from EBay.
I mixed this (carefully ) and tried this. The negs were still thin, but better, and with a light stain.
I then tried 1+1+50 and got a further improvement but it was still short of a few that I'd developed in PMK, both in density and stain in the upper values.

Then it got to the point I was wasting too many sheets, and had real subjects to take, so I cut losses and mixed up more PMK from the stocks I had.
However tthe WD2H A and B are still there, waiting for me to figure out what to try next.

I would appreciate someone else having a go !
John was struggling to remember enough to advise, given that he doesn't have all of the notes from 25+ years ago when he did the last reformulation.

[Michael R]

If I remember correctly the H formula was more dilute than the D version, the goal being more contrast/stain for the petroglyph negatives he was making at the time, so maybe it needs longer development times?


I did Alan, I mixed some up early this year and tried using it. I agree that the dilution seems to be 1+1+64.
( ps. i still don't believe there is such a thing as WD2H+ , I think it's WD2H. It's confused by there being WD2D+ before it )
...Anyway, then the story gets messy. I got a very thin couple of negs from the first mix. I talked to John Wimberley ( we were corresponding already re. the Durst 138S ) for de-bugging ideas and then got a pH meter and tested the B solution, then the full developer mix, both were too low, not alkaline enough.
I concluded that there was either an error in the sodium carbonate that I'd been sold, or I had mixed the wrong dilution somehow.
I then bought some more carbonate from EBay.
I mixed this (carefully ) and tried this. The negs were still thin, but better, and with a light stain.
I then tried 1+1+50 and got a further improvement but it was still short of a few that I'd developed in PMK, both in density and stain in the upper values.

Then it got to the point I was wasting too many sheets, and had real subjects to take, so I cut losses and mixed up more PMK from the stocks I had.
However tthe WD2H A and B are still there, waiting for me to figure out what to try next.

I would appreciate someone else having a go !
John was struggling to remember enough to advise, given that he doesn't have all of the notes from 25+ years ago when he did the last reformulation.

[Mark J]

Seemingly, but however John gave all of the info at the time it was posted here ( 2011 ) , I just checked my copy and it was 9.5 mins for FP4+ for an N development at 70°C.

[Eric Woodbury]

I use WD2H+ for pushing FP4+ to the limit. I mix my own according to Anchell's Darkroom Cookbook and the times therein. Negs are good.

NOTE: Solution A needs 60 grams of pyrogallic acid that is not shown. A mistake in the book. Without it you have really crummy D23.

[Mark J]

John said that the 'cookbook' missed out the sodium bisufite, 20g . Not the pyrogallol.
When I get time I'll dig out the link to his posting.

[Alan9940]

Thought I'd pass on my findings...so far.

I developed an 8x10 sheet of Fomapan 100 this morning in a BTZS tube at 20C for 8 mins; 1+1+64 dilution. It's hanging to dry as I type this, but it appears just a tad thin to me. However, I seem to recall from back about 100 years ago when I used the original WD2D formula that these negs always looked kinda thin. I won't know until I print it. My initial trial time may have been a little short, but I went that way because in my experience Fomapan 100 tends to build contrast quickly, and I really didn't know what to expect here.

[Mark J]

Very interesting, thanks. I had picked up a couple of old postings about WD2D/+ being 'thin' .

[Eric Woodbury]

Solution A
Benzo 0.2g
Metol 6g
Na Bisulfite 20g
Pyro 60g
EDTA 5g
Water 1 liter

Solution B
Na Carbonate 110g
Water 1 liter

Use Distilled water for mixing concentrates.

[Mark J]

https://www.largeformatphotography.info/forum/showthread.php?59085-Wimberly-WD2D-and-Jobo-Rotary-Processing-Heaven!

[Mark J]

Alan, we must try and work on this problem - because I have over £20-worth of Pyrogallol locked up in that 250ml 'A' bottle !

Looking back at the formula, I can see that one of the differences between the WD2D and H , comparing to PMK, is that they use a lot more Sodium Bisulphite : it's 3:1 Pyrogallol to Bisulphite in the WD developers, and 5:1 in PMK. Maybe one of the chemistry experts can comment on what difference that makes ?

[Alan9940]

Mark, I found in the printing of my neg that it was indeed quite under-developed. Honestly, I hate testing this kind of thing when I already have other developer formulas that I'm satisfied with. I had mixed only a small amount of WD2H so I'm not concerned if I toss it someday. Who knows? I'll leave it sitting on the shelf and, maybe, some day in the future I'll get the itch to experiment further with it.

Good luck and pass on any info you discover.

[Mark J]

Fine, I understand ; let's see if anyone else comments. I can do some maths in the near future and work out how to make a larger bottle of 'A' solution that adds more water, Metol and Pyrogallol but no Bisulphite .
I will also ping John W one more time, for comments.

[Michael R]

For reference, here is a comparison of the contents of working solutions of WD2D, WD2H and PMK. I've excluded the EDTA-Na4 as it is sometimes there, sometimes not. WD2D originally had different dilution recommendations for roll and sheet film, the sheet film being the more concentrated end of the range.

I have not measured the pH values. Hutchings claimed PMK is 9.6. The Wimberley developers should be somewhat higher, which makes the working solution less stable without more sulfite. More sulfite means less stain (all other things being equal), however note WD2H has less sulfite than WD2D and in fact the sulfite and developing agent concentrations of WD2H are essentially the same as PMK.

I have not tested the Wimberley developers myself but a different stain color than PMK is claimed due to the different alkali and/or alkalinity.

PMK seems to temper highlight contrast somewhat. This would tend to allow for more development which could result in slightly better film speed than other pyrogallol developers. It is possible this could have to do with a reaction between the metaborate and pyrogallol which reduces activity. This reaction between borate and ortho-hydroxybenzenes has been reported in the literature but I don't know if Hutchings knew about it.

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[Mark J]

Thanks for putting that together Michael.
I went part-way through something similar when I got the first results from WD2H.

I'm not sure I can agree with you that the sulphite-to-developer ratios are essentially the same. I'm still seeing 30 to 35% for the WD developers and 20% for PMK. If as I suspected ( and you confirm) , the sulphite reduces stain, then that seems like the only explanation for what I've seen, which is distinctly less stain on Fomapan 200 with WD2H , even in increased concentration. In fact there is hardly any stain, which make it rather pointless to use !

This goes against what I'd expected from the Wimberley developers, where John had said that the more alkaline 'B' solution with the carbonate would allow the stain to develop more fully, in contrast to PMK.
I think the pH of WD2H ( which I tested during the problems ) is around 9.8 or 9.9
However it looks to me like the extra sulphite ( aka sulfite ) is working against this.

The main reason I wanted to try WD2D+ or WD2H was that the stain is supposed to be more yellow/brown, rather than greenish with PMK, which ought to work better with VC paper.

I suppose i could still try something with less sulphite, like a PMK 'A' , with the carbonate 'B' solution ? Presumably some of the the issue with stability is about using the developer soon enough, which I do anyway ( typically 2mins from mixing to deploy ) ...
Unlike John, I'm not currently doing long development times for N+3 or 4 as John was with the petroglyph photos.

[Michael R]

Thanks for putting that together Michael.
I went part-way through something similar when I got the first results from WD2H.

I'm not sure I can agree with you that the sulphite-to-developer ratios are essentially the same. I'm still seeing 30 to 35% for the WD developers and 20% for PMK. If as I suspected ( and you confirm) , the sulphite reduces stain, then that seems like the only explanation for what I've seen, which is distinctly less stain on Fomapan 200 with WD2H , even in increased concentration. In fact there is hardly any stain, which make it rather pointless to use !

This goes against what I'd expected from the Wimberley developers, where John had said that the more alkaline 'B' solution with the carbonate would allow the stain to develop more fully, in contrast to PMK.
I think the pH of WD2H ( which I tested during the problems ) is around 9.8 or 9.9
However it looks to me like the extra sulphite ( aka sulfite ) is working against this.

The main reason I wanted to try WD2D+ or WD2H was that the stain is supposed to be more yellow/brown, rather than greenish with PMK, which ought to work better with VC paper.

I suppose i could still try something with less sulphite, like a PMK 'A' , with the carbonate 'B' solution ? Presumably some of the the issue with stability is about using the developer soon enough, which I do anyway ( typically 2mins from mixing to deploy ) ...
Unlike John, I'm not currently doing long development times for N+3 or 4 as John was with the petroglyph photos.

It’s really the concentration of sulfite in the working solution rather than the ratio of sulfite to pyrogallol that affects stain. The difference between 0.2 and 0.3 g/l is small. All other things being equal, a sulfite concentration of 0.3g/l should allow for significant imagewise stain. U haven’t used Wimberley’s developers so I don’t know what the negatives are supposed to look like. Imagewise stain can sometimes be difficult to evaluate visually. I suggest trying to print the negatives and/or taking some densitometer readings through a blue filter (or the blue channel on a colour densitometer) to get an idea of how much density there is.

[Mark J]

OK. I haven't got a densitometer ( we used to have one at work but it's been retired ) .
I keep thinking about it but find it hard to justifiy approx £1000 for a current one with a blue channel option.

I have negs from WD2H and PMK on the same scene on the same day, I just need to dig out the correct pair ( there was some initial trouble with a suspect mix of carbonate ) .
Hence I can compare , knowing what I'm used to from PMK over the years. Even with a 10% increase on concentration on the A and B , the WD2H negs fell well short of the visual density of the PMK ones.
I will try & take a shot to illustrate if I can get the negs & info together.

[Michael R]

It’s interesting you’re saying visually the WD2H negatives are noticeably thinner than the PMK negatives of the same scene. Even if we leave aside the difference in staining, if the silver density is noticeably thinner and contrast is the same I’m puzzled by that, because it would mean a big speed loss from WD2H relative to PMK, which I would have trouble explaining. On the other hand if both the density and contrast are low maybe the development time needs to be extended (which would also increase stain).


OK. I haven't got a densitometer ( we used to have one at work but it's been retired ) .
I keep thinking about it but find it hard to justifiy approx £1000 for a current one with a blue channel option.

I have negs from WD2H and PMK on the same scene on the same day, I just need to dig out the correct pair ( there was some initial trouble with a suspect mix of carbonate ) .
Hence I can compare , knowing what I'm used to from PMK over the years. Even with a 10% increase on concentration on the A and B , the WD2H negs fell well short of the visual density of the PMK ones.
I will try & take a shot to illustrate if I can get the negs & info together.

[Mark J]

OK I should clarify, the Zone 2 detail on the WD2H ones was nearly the same as the PMK ones, so i don't think there's a fundamental loss of speed; they just look under-developed.

[Mark Sampson]

Thime for a Proper Proof or two. Never mind how the negatives "look", see how they perform.

[Michael R]

OK I should clarify, the Zone 2 detail on the WD2H ones was nearly the same as the PMK ones, so i don't think there's a fundamental loss of speed; they just look under-developed.

Thanks for clarifying that - that’s good news in that it might simply mean you need to significantly extend development time with WD2H. That would make sense to me relative to WD2D since WD2H is twice as dilute, but it would be surprising to me if the WD2H development time needed to be much longer than PMK since they contain basically the same concentrations of developing agents and the pH of WD2H should be higher than PMK.

I hope you are able to figure this out.

[Mark J]

(Edit : this reply to Mark, not to Michael ) :

Oh I already did a print from one of the negs exposed with a slightly more concentrated mix.
It was fine, but the subject wasn't all that demanding in terms of range or subject properties.

The problem will be when I have subjects like bright clouds or texture on high-value water, where I need the negs to be showing a decent level of staining to get the Pyro advantages.
I'm not intending to go ahead with a Dev process that only uses about 2/3rd of the potential neg density range. I'm not into hauling around 5x7" gear just to get some 'decent' pics.
ps. I've been using PMK for 26 years , I know what the neg should look like, and given WD2H is not that different, it should look at least close , but with a different stain colour.

[Mark J]

Thanks Michael, yes.
I'll have a good look at the numbers ref WD2D and WD2H and have another go with an 'educated guess' at what might work.
I will probably also try the experiment with PMK 'A' plus the Sodium carbonate 'B' for kicks.

One factor in all of this that may be skewing the results, is that John was exclusively using FP4+ for all of his work and experiments, and it's clear that FP4+ stains more than Fomapan 200.

[Eric Woodbury]

If you really want some range, you can split the developer. I've done this with PMK. Without a rinse, soak film in PURE SOLUTION A for 3 minutes, then use Solution B diluted for various times as needed. It's like split D23 or others. Strong shadow details and huge dynamic range. You can shoot indoors and the details coming through the windows won't saturate.

[Michael R]

Thanks Michael, yes.
I'll have a good look at the numbers ref WD2D and WD2H and have another go with an 'educated guess' at what might work.
I will probably also try the experiment with PMK 'A' plus the Sodium carbonate 'B' for kicks.

One factor in all of this that may be skewing the results, is that John was exclusively using FP4+ for all of his work and experiments, and it's clear that FP4+ stains more than Fomapan 200.

Well, if you use PMK A with a carbonate B it’s essentially WD2H but it’s always worth a try. With the higher alkalinity of carbonate fog and non-imagewise stain would be expected to increase, but I don’t know by how much. Presumably that’s why John included a small amount of restrainer.

Let us know what you find. It’s possible there’s something Fomapan 200 doesn’t like about WD2H, although I’m not sure what that could be.

[Mark J]

Well, if you use PMK A with a carbonate B it’s essentially WD2H
Aside from the stain colour and its effect on density - which was part of the interest.
https://sandykingphotography.com/an-intro-to-pyro-staining-developers/

[Michael R]

Aside from the stain colour and its effect on density - which was part of the interest.
https://sandykingphotography.com/an-intro-to-pyro-staining-developers/

The working solutions of PMK and WD2H are virtually identical (+/- slop) in their part A composition. The difference is the alkali. If you replace the PMK alkali with carbonate you have WD2H.

Incidentally be careful with contemporary writing about tanning/staining developers. It’s mostly regurgitating ancient mythology.

[Mark J]

I suspected that you would eventually turn against the subject, Michael.
Good that you are, however, warning us callow impressionable youths against the dangers of getting too tied up in staining developers.

[interneg]

The working solutions of PMK and WD2H are virtually identical (+/- slop) in their part A composition. The difference is the alkali. If you replace the PMK alkali with carbonate you have WD2H.

Incidentally be careful with contemporary writing about tanning/staining developers. It’s mostly regurgitating ancient mythology.

What's also interesting is that almost all of the characteristics attributed to the stain really have more to do with low metol concentrations at specific pH ranges (and/ or P:dihydroxybenzene ratios) - and that this has been known about for decades within the industry (and commercially exploited), but is apparently much less interesting than dying your negs a funny colour with a potentially rather risky poison. There's a lot that could be done with Beutler derivatives - but that might require a much more clear eyed approach to how visual outcomes really relate to the chemistry of the developer rather than mantric repetition of various weekend workshop gurus.

[Michael R]

Mark,

I’m not turning against the subject and I think it’s a worthwhile investigation. Hopefully you are able to sort out WD2H.

[Mark J]

Ah, I was thinking back to the way some of your discussions with DREW have developed, regarding staining developers.

[Mark J]

There's a lot that could be done with Beutler derivatives -
And do these developers also reduce the grain-scatter ( Callier effect ) in upper mid-tones and highlights ?

[Mark J]

Michael, that little table you did earlier is v. interesting and food for thought. It looks sensible to try a more significant increase in the amounts of A and B on my next try, given how much appears to be used in WD2D. I only tried about 10% more last time, plus later a small extension in the dev time.
One thing I spotted though, is that there is benzotriazole in WD2D as sold by Photographer's Formulary, but it's in the 'B' solution.

Let's see if I can get a couple of shots at the weekend.

[Michael R]

Ah, I was thinking back to the way some of your discussions with DREW have developed, regarding staining developers.

Oh ok I see now... :) yes my discussions with Drew might appear quite confrontational - however it's mostly us teasing eachother about long-standing disagreements about certain things so at this point it's exaggerated, friendly jabbing. We've got a history here and on the old APUG, but neither of us have ever taken it seriously or had hard feelings. There are even some things we agree on.

[Michael R]

Michael, that little table you did earlier is v. interesting and food for thought. It looks sensible to try a more significant increase in the amounts of A and B on my next try, given how much appears to be used in WD2D. I only tried about 10% more last time, plus later a small extension in the dev time.
One thing I spotted though, is that there is benzotriazole in WD2D as sold by Photographer's Formulary, but it's in the 'B' solution.

Let's see if I can get a couple of shots at the weekend.

You're probably right about the Benzotriazole in WD2D. There have been a few versions of WD2D over time. I recall John saying the original version contained Benzotriazole but that he later omitted it. Then there's the "WD2D+" Formulary sells, which I think excludes Benzotriazole but adds the EDTA. The formula for WD2D+ has never been disclosed though, so aside from omitting Benzotriazole, we can't be sure about whether or not it is otherwise the same as WD2D.

WD2H ends up being essentially the equivalent of using half the concentration of WD2D part A in the working solution. Since John's original motivation for WD2H was maximum contrast, I assume he arrived at the conclusion the more dilute solution would generate more imagewise stain.

I'm curious to know what you find out in your tests. Actually I wouldn't mind experimenting a little myself (for example to find out if the difference in alkali actually changes the colour of the stain), but I'm not sure when I'd get around to it.

[interneg]

And do these developers also reduce the grain-scatter ( Callier effect ) in upper mid-tones and highlights ?

There's very little good evidence of the pyrogallol actually having meaningful tanning effects on very well hardened emulsions. The observable effects on negatives people associate with tanning may have more to do with the dye formation (cf. Kodachrome which produced similar relief despite having no tanning steps in the process) than any real printing effect, other than the colour produced - developers intended for properly tanning unhardened matrix emulsions had much higher pyrogallol concentrations - and the level of oxygen scavengers within a given set of sensitised emulsions will have a significant effect on the amounts of dye something like Pyrogallol can form. Scattering effects have been very deeply researched by the manufacturers (e.g. microdensitometry of exposures done with X-rays etc) - if pyrogallol (or any other tanning developers) really worked like people wish they did, they would never have fallen out of use. What is based in measurable and observable fact is that very low metol concentrations (i.e. working solution contains 0.5g/l or lower) produce an array of potentially useful effects via exhaustion of the metol - higher edge sharpness and much more controlled highlight density (which has knock-on effects on perception of granularity, especially in relatively smaller enlargements) being the particularly apposite ones here. The same effects can be achieved in PQ (or PC, but no good reason to use it) and Phenidone Ascorbate developers in commercially applicable and even more controllable ways (if you have R&D backup for getting it truly zero'd in). Commercial applications have tended towards wanting to balance grain/ speed/ sharpness characteristics differently (needs to optimise reasonably equally perceptually across 1-40x) from where those making 3-4x enlargements off sheet film for 'fine-art' applications may wish to go - the latter category may have ended up somewhere useful enough for their usage from poorly controlled trial and error, but often seem to errantly attribute beneficial effects to other phenomena and/ or are making the developers far more complicated than they need to be.

[Mark J]

Is there a connection between tanning and the Callier effect/coefficient, which was the subject I cited ?

[Eric Woodbury]

I doubt it. Tanning is a dye form. It is smooth and continuous to a degree smaller than wavelengths of visible light. No ability to scatter. Callier is caused by scattering.

[Michael R]

Is there a connection between tanning and the Callier effect/coefficient, which was the subject I cited ?

In general, assuming the negative is being enlarged/projected, and that you do so with a collimated light source, I think there should be an inverse relationship between the overall Callier effect and the proportion of stain (dye) forming the optical (printing) density. Tanning in and of itself should not really be related to the Callier effect. For a given total optical density, the more dye there is, the lower the overall Callier effect should be, although I don’t know what the curve of Q values looks like for a mixed silver-dye negative.

In the case of a B&W negative film processed in a staining developer, there is still quite a lot more silver than dye forming the image, so my guess is that while a stained negative would probably have measurably lower Callier Q values at higher densities versus an all-silver negative, I’d expect the overall difference in Callier effect to be relatively small, especially if the light source isn’t highly collimated to begin with.

You could test this. It would require some work.

[Mark J]

My impression from what I printed in 1999 from conventional vs. PMK negs is that the reduction in Callier coefficient is very significant in terms of the rendition of higher values and specular highlights.
Printing from a collimated light source is hardly ever possible, and this is the nub of the issue, with diffuser heads especially, the incoming light is maybe 160° cone angle or so, this is where the stained negative shows the most advantage.

[Michael R]

That’s puzzling to me. While an image formed with some dye and silver should have a smaller Callier effect when projected than an image formed entirely with silver (all other things being equal), to begin with the Callier effect (or Q factors > 1) is the scattering of collimated incident light by silver the silver particles. If the light incident on the negative is already scattered/diffuse, there should be no significant Callier effect whether the image is formed by silver or dye.

This all appears to be the opposite of what you observed, so I’m not sure what to make of it. Maybe something else is going on. Not sure how you did the comparisons etc. It’s a tedious thing to test. It seems to me you need to begin with a stained and non-stained negative that contact-print to produce equal contrast prints (or enlarging with a diffused source might serve well enough). That becomes your “control” setup. Then you projection-print the same two negatives with a collimated light source and see if they still print with the same contrast or not.

Of course there’s also the possibility I’m mixing things up as it’s been a long time since I’ve read about the Callier effect, so hopefully I haven’t derailed things.

[Mark J]

I'll try & explain what I mean. It may take a couple or three postings. I can't offer much in terms of proof or quantitative measured, this is qualitative from negs and prints, however I do have some opinions about what is going on in terms of the science. My concept of what happens was clarified a little recently, when re-printing existing negs on a condenser, rather than diffuser enlarger head.

Gordon Hutchings discusses the 'reduction of the Callier effect' on page 49 of his Pyro book, but oddly he gets the pros/cons of diffuser vs. condenser head the wrong way round.

First, I want to show an optical model of condenser illumination, just to comment on your use of the term 'collimated incident light'. The model below is one I put together on CodeV from measurements of the components and spacings on the Durst 138S. The source set-up here is my own case of a 100x100 opal diffuser placed about 20mm from the rectangular 85x75mm aperture of the lamp box.
I wanted to analyse what was the cone angle of light reaching each point on the neg.
The glass carrier and neg plane is close and underneath the big condenser lenses.

First, one point is that the condenser set-up angles the light around as you go further out in the neg - this is so that the light is 'aimed' at the enlarger lens - and why you need to swap condenser lenses sometimes if printing at a very low or high magnification.
In this set-up, you can see that the cone of light going to each point on the neg is relatively narrow. It is between 20° and 22.5° total angle.
Some might say this is semi-diffuse, but the light from a diffuser box would probably expose each point on the neg to a cone of at least 150° , so there is still a big difference.

A smaller bulb, or a point-source, would create a cone much narrower than 20°, but by doing this it would also highlight dust and scratches on the upper neg glass much more.

250129

[Mark J]

If the light incident on the negative is already scattered/diffuse, there should be no significant Callier effect whether the image is formed by silver or dye.


I should probably stop using the term 'Callier effect' in further explanations, because I am likely to be mis-using it. I think that Callier effect strictly refers to the loss of overall contrast in going from a contact print to an enlarged print. It is cause by scatter, so I will just use the word scatter.

Just to continue explaining this from the standpoint of different types of neg illumination, the view up from the negative towards the enlarger source is similar in some ways in the case of a condenser head and a diffuser head ; in that, there is a uniform bright patch of light that is incoherent ( in physics terms ). It's just that in a condenser head, this patch of light is some distance away, and small in angular terms , whereas from a diffuser head, the light fills nearly a hemisphere. It's not a case that one is 'already diffused' while the other is not. It's just that they subtend different angles.

On the other side of the system, we can say that there's no argument about how the light from the underside of the emulsion proceeds to the paper - whatever emerges from the neg and is heading towards the entrance pupil of the enlarger lens will be focused and appear on the paper.

So the bit that interests me, and I think can explain the difference we see in prints from stained and non-stained negs, and between condenser and diffuser-printed pictures, is the bit in the middle - what happens to the light in the film base and particularly in the emulsion.

I really need to draw a couple of pictures to do this properly, but that will take some time, so i will put down some words first.

I believe that what distinguishes the above cases, and how the prints look, is the amount of lateral scatter of the light in the emulsion.

[Michael R]

Mark, thanks for the detailed follow-up. I’m going to need to go through it and think some more to make sure I understand it.

One quick thing I wanted to clarify. The Callier effect is the increase in contrast when going from contact to projection with a collimated (to varying degrees) light source. When a negative is projection-printed, if the emulsion scatters light (ie silver vs dye), the more collimated the light incident on the film, the greater the overall difference in attenuation between low and high densities (ie the greater the printing contrast). For example given a silver negative, printing contrast is higher using a point source head than a diffusion head.


I should probably stop using the term 'Callier effect' in further explanations, because I am likely to be mis-using it. I think that Callier effect strictly refers to the loss of overall contrast in going from a contact print to an enlarged print. It is cause by scatter, so I will just use the word scatter.

Just to continue explaining this from the standpoint of different types of neg illumination, the view up from the negative towards the enlarger source is similar in some ways in the case of a condenser head and a diffuser head ; in that, there is a uniform bright patch of light that is incoherent ( in physics terms ). It's just that in a condenser head, this patch of light is some distance away, and small in angular terms , whereas from a diffuser head, the light fills nearly a hemisphere. It's not a case that one is 'already diffused' while the other is not. It's just that they subtend different angles.

On the other side of the system, we can say that there's no argument about how the light from the underside of the emulsion proceeds to the paper - whatever emerges from the neg and is heading towards the entrance pupil of the enlarger lens will be focused and appear on the paper.

So the bit that interests me, and I think can explain the difference we see in prints from stained and non-stained negs, and between condenser and diffuser-printed pictures, is the bit in the middle - what happens to the light in the film base and particularly in the emulsion.

I really need to draw a couple of pictures to do this properly, but that will take some time, so i will put down some words first.

I believe that what distinguishes the above cases, and how the prints look, is the amount of lateral scatter of the light in the emulsion.

[interneg]

When a negative is projection-printed, if the emulsion scatters light (ie silver vs dye), the more collimated the light incident on the film, the greater the overall difference in attenuation between low and high densities (ie the greater the printing contrast). For example given a silver negative, printing contrast is higher using a point source head than a diffusion head.

Which seems exactly contradictory to the standard claim about staining developers - that they make highlights easier to print - aka less dense (yet seemingly sharper). More intense adjacency or exhaustion effects than D-76 produces will both intensify apparent edge definition and hold highlight density dramatically more under control (DIR couplers do the same thing even more spectacularly so in chromogenic negative films) - which will effectively lower apparent granularity and still make edges seem apparently sharper. The true causes of these effects in B&W seem to have been well known to the major research labs and steadily commercialised for several decades (often quite slowly however) - and has nothing to do with the dye formed, but a lot to do with the other components in these developers. As for the UV effects of the dye formed, I think many people would do well to look at the spectral characteristics of a yellow-green filter (Wratten #11 is a good one) which gives a rather stark illustration of potential UV blocking characteristics of dyes in the region of PMK's colour.

[Mark J]

I can't see how you can increase the contrast ( with a fixed light source colour/grade ) from a contact print situation, by going to any form of enlargement. Contact printing pretty much has the maximum directionality of the light reaching the negative - because it is illuminated by a small distant lens pupil that might be 2 or 3 feet above the neg.

There is a thread here in the UK where I showed how i worked through my thoughts on this.

This is where I joined, but I was late to the party -
http://www.film-and-darkroom-user.org.uk/forum/showthread.php?t=14020&page=6

There are print scans near the end.

[Michael R]

Which seems exactly contradictory to the standard claim about staining developers - that they make highlights easier to print - aka less dense (yet seemingly sharper). More intense adjacency or exhaustion effects than D-76 produces will both intensify apparent edge definition and hold highlight density dramatically more under control (DIR couplers do the same thing even more spectacularly so in chromogenic negative films) - which will effectively lower apparent granularity and still make edges seem apparently sharper. The true causes of these effects in B&W seem to have been well known to the major research labs and steadily commercialised for several decades (often quite slowly however) - and has nothing to do with the dye formed, but a lot to do with the other components in these developers.

All things being equal, dye clouds scatter much less light than silver particles (which is why colour/chromogenic films how show minimal/no Callier effect as far as I’m aware). Since a negative processed in a staining developer has less silver for a given density, in theory the stained negative should exhibit a smaller Callier effect than an all-silver negative. How much less, I don’t know. As I speculated earlier, probably not a huge difference since there is still a lot more silver than dye forming the image, but it would have to be tested. Objective testing could be done but it is tedious work.

[Mark J]

Picking up on what Interneg has just said.
I contend that the key difference in both mids and highlights in staining-developer negs is not about a difference in density , but that they are less scattering. Hence there is more local contrast ( and MTF ) even if they are the same density as a grain-only neg. That's what I see.

I have two near identical negs from 1999 that i will try to selectively print next time I am in the darkroom.

[interneg]

Since a negative processed in a staining developer has less silver for a given density, in theory the stained negative should exhibit a smaller Callier effect than an all-silver negative. How much less, I don’t know. As I speculated earlier, probably not a huge difference since there is still a lot more silver than dye forming the image, but it would have to be tested. Objective testing could be done but it is tedious work.

I think any nominal difference in Callier effect between stained and non stained is probably vanishingly small, and probably has much more to do with inhibition/ exhaustion effects overall. I do wonder how many people will recognise that the comparator has to be the Beutler formula (modified to use Kodalk) and not some other random developer...

[Michael R]

Thanks, Mark. I’ll have a look at this.

Yes on the surface it seems somewhat counterintuitive that scattering effects result in increased overall contrast when the light source is collimated. This is reflected in the formula for the Callier Q factor, which for a given amount of developed silver is the attenuation of collimated light divided by the attenuation of diffuse light, and the Q factor is always >=1. Some diagrams could help here but I’m stuck at work late…


I can't see how you can increase the contrast ( with a fixed light source colour/grade ) from a contact print situation, by going to any form of enlargement. Contact printing pretty much has the maximum directionality of the light reaching the negative - because it is illuminated by a small distant lens pupil that might be 2 or 3 feet above the neg.

There is a thread here in the UK where I showed how i worked through my thoughts on this.

This is where I joined, but I was late to the party -
http://www.film-and-darkroom-user.org.uk/forum/showthread.php?t=14020&page=6

There are print scans near the end.

[Mark J]

I think any nominal difference in Callier effect between stained and non stained is probably vanishingly small, and probably has much more to do with inhibition/ exhaustion effects overall. I do wonder how many people will recognise that the comparator has to be the Beutler formula (modified to use Kodalk) and not some other random developer...

Well it's not very small - otherwise I wouldn't have ditched conventional developers in 1999 and used PMK mainly since then.
However my comparison was only against my usual developer at that time, which was Perceptol 1+2.
I just had a look for the Beutler formula, because I've not seen it widely discussed, luckily John Finch had a page about it.
What are the differences between Perceptol 1+2 and Beutler in practical terms ?. Am I right that Perceptol is also a metol-only developer ?

[interneg]

Well it's not very small - otherwise I wouldn't have ditched conventional developers in 1999 and used PMK mainly since then.
However my comparison was only against my usual developer at that time, which was Perceptol 1+2.
I just had a look for the Beutler formula, because I've not seen it widely discussed, luckily John Finch had a page about it.
What are the differences between Perceptol 1+2 and Beutler in practical terms ?. Am I right that Perceptol is also a metol-only developer ?

From all the available evidence Perceptol/ Microdol stock solution is 5g/l metol - therefore 1+2 is 1.67g/l Metol. Beutler is 0.5g/l metol at working strength, and this is the point at which Metol can be seen to have viable (both statistically and clearly visible) exhaustion effects of consequence to sharpness and highlight density.

Beutler and Microdol/ Perceptol share a common root (5g Metol, 100g sulphite), but go in different directions for various reasons.

There is a destructive test that would demonstrate if there was truly any meaningful tanning happening (doubtful on any emulsion that's already incredibly well hardened with vinyl ethers - which are very, very difficult to damage).