Stain, dye clouds, sharpness - question for the chemists

Discussion in 'B&W: Film, Paper, Chemistry' started by michael_r, Dec 28, 2012.

  1. michael_r

    michael_r Subscriber

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    Warning - this is not a Pyro war. Just a question about the dye formed. And it could possibly apply to colour/chromogenic films. Not sure.

    So, we "know" that generally, Pyro/Cat developers are considered sharp. There are a variety of reasons for this including low solvent action (at least in staining formulas), adjacency effects, tanning etc. In a staining formula, since the image is composed of silver and dye density, why doesn't the dye cloud formed around each silver grain (or group of grains) reduce sharpness? Isn't the dye cloud effectively "spreading out" around the grain of developed silver?

    Michael
     
  2. Gerald C Koch

    Gerald C Koch Member

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    It actually does reduce sharpness. The same thing occurs in a true chromagenic film. This can be seen in photomicrographs of stained negatives. If you think about it this has to occur because if the stained area was the same size as its grain then you wouldn't see it. The silver grains would act as masks. How far the stain extends past the silver grain is a function of the developer composition and the diffusion rate of the oxidized developer. This is why staining developers are not recommended for SF films. For MF and LF format negatives the loss of sharpness is countered by the reduced appearence of the grain. But then grain is really not a problem in these formats.
     
  3. michael_r

    michael_r Subscriber

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    Thanks, Gerald. Makes sense. After all you can't get the "grain masking" effect without the dye spreading beyond the edges of the silver grains, clumps of grains etc. Although I have to say in my experience the grain masking effect is less than one might expect, even with fairly heavy stain.

    Interesting how formulators of staining developers often refer to the grain masking effect, but I can't recall any mention of any offsetting effect on apparent sharpness or possibly even resolution. You're apparently supposed to have your cake and eat it.

    Thanks
    Michael
     
  4. Gerald C Koch

    Gerald C Koch Member

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    Michael, staining developers are one of those aspects of photography that has taken on semi-religious or mystical overtones.

    The stain helps make the edges of the grains less pronounced.
     
  5. Ian Grant

    Ian Grant Subscriber

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    The problem here is that theory and hypothesis aren't the same as the actual practical results. Not all staining developers are the same the older more concentrated types don't give fine grain but their degree of acutance/sharpness from the tanning effects made them ideal for contact prints.

    The newer highly dilute Pyro developers are quite different, they give sufficient staining and acutance without compromising grain etc, it's a balance.

    Pyrocatechin is used in fine grain developers, on it's own or in combination, sometimes with levels of sulphite that suppress staining, so a developer like Pyrocat HD/MC would almost certainly give good fine grain regardless of the staining.

    Maybe the staining's sufficient t mask the edges of the grain but it's not having a detrimental effect on the micro contrasts which affect the fine details.

    Ian
     
  6. Gerald C Koch

    Gerald C Koch Member

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    The question of resolution can be argued ad nauseum until someone steps up and runs a series of well designed and executed experiments comparing a staining developer against an acutance developer using a standard resolution chart.
     
  7. Ian Grant

    Ian Grant Subscriber

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    It's the final prints that count not testing with resolution charts which only tell you part of the story. I'm just cutting mats for 50+ exhibition prints all from Pyrocat negatives and it's the balance of sharpness (definition), tonality etc and rendition of detail in highlights and shadows that's important to me. I should add my Pyrocat negs scan wee to.

    Ian
     
  8. Gerald C Koch

    Gerald C Koch Member

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    If no one runs the experiment I suggested then the argument about the resolution of staining devellopers is a moot point and this thread is immaterial.
     
  9. Ian Grant

    Ian Grant Subscriber

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    But it doesn't address the realities, I guess I've done the tests and seen the results for myself but not in a lab/false situations.

    I tried and used many of the older high acutance developers, Hyfin, Acutol-S and a few others. sure they give superb acutance and sharpness but grain isn't fine and tonality is harsh and you can lose fine detail.

    Real life testing is far more important.

    Ian
     
  10. Kirk Keyes

    Kirk Keyes Member

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    Part of the "magic" of staining developers when compared to chromogenic films is that the stain actually hardens the film adjacent to the area of development. This hardening is said to reduce the amount of growth/spread of the silver, making the image sharper.

    Chromogenic films just generate dye clouds, without the benefit of the hardening effect.

    I believe Sandy King posted info on resolution tests he had done with his developers here years ago.
     
  11. Ian Grant

    Ian Grant Subscriber

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    That's a good summary Kirk.

    Those effects are of course substantially greater with the older Pyro formulae in use from the late 1800's through to about WWII when their use had largely ceased.

    I've two interesting articles in BJP Almanacs on the use of modern Pyro developers, same autor but a few years apart. Ilford published a developer similar to Pyrocat HDbut using Pyrogallol in a Patent in fact it was a Phenidone variant of a Metol-Pyrogallol developer. The major difference is the dilution.

    Windisch's Fine grain compensation developer is a Pyrocatechin based staing developer with excellent resolution.

    Ian
     
  12. michael_r

    michael_r Subscriber

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    But the effect Kirk refers to is the tanning I mentioned in the original post, which is separate from staining. So I assume, all other things equal (solvent effect etc), a formula producing a heavy stain is less "sharp".

    It would be interesting to make prints from the stained (imagewise) negatives after bleaching away all the silver. I wonder if the printed image would be sharp to the eye.
     
  13. Bob Carnie

    Bob Carnie Subscriber

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    Or try making a print from the same series, one stained , one not.. I have done this and the non stained image if I remember correctly looked grainier and possibly sharper.

    I was convinced for a lot of Richard Avedon's work on grey background was unstained pyro development.

    btw I believe the tannin effect is probably the silver bullet of Pyro developers.

    QUOTE=Michael R 1974;1440106]But the effect Kirk refers to is the tanning I mentioned in the original post, which is separate from staining. So I assume, all other things equal (solvent effect etc), a formula producing a heavy stain is less "sharp".

    It would be interesting to make prints from the stained (imagewise) negatives after bleaching away all the silver. I wonder if the printed image would be sharp to the eye.[/QUOTE]
     
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  15. Kirk Keyes

    Kirk Keyes Member

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    From one survivor of the pyro wars to another, thanks!
     
  16. Kirk Keyes

    Kirk Keyes Member

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    I'd say tanning and staining are the same thing, just different words used to decribe different effects of the pyro on the gelatin. Tanning refers to the physical hardening of the gelatin from the action of pyro developers, staining is the colored by-products generated from the action of pyro developers on the gelatin.

    I've bleached the silver out of pyro-developed negs to measure the stain density present without the silver present. (Actually, I've done it with Tmax 100 developed in XTOL, and it has a very faint stain present too, but it's very faint and probably not of any practical use.)

    I never tried printing these negs (I actually cut then up so I could scan them in a spectrophotometer...), but I seem to remember Patrick Gainer making prints from such negs.

    More stain makes more hardening, which I think would create sharper negs. But that's just a guess. Seems like something to test...
     
    Last edited by a moderator: Jan 2, 2013
  17. michael_r

    michael_r Subscriber

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    Kirk - are you sure you're right about this? My understanding is the stain has more to do with developer oxidation products (and it would seem the type of alkali plays a role here as well - influencing the stain colour to some extent).

    For example, if we add sulfite we reduce/eliminate imagewise stain, but is the gelatin hardening effect also reduced/eliminated?

    PS: I remember coming across some of those Pyro war threads not too long ago when I was searching for something (they were before my time). Wow did that ever get ugly!!

    Thanks
    Michael


     
  18. Philippe-Georges

    Philippe-Georges Member

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    - What is exactly the difference between TANNING and STAINING in Pyro development?
    Does the tanning results in staining or vice versa, or is staining completely different/independent from tanning, or is staining some kind of tanning or vice versa?

    - Right now I am scanning(*) the to me best negatives I made from 1992 till now, and the negs developed since 2006 in Pyro-HD (S. King) are showing better scanning results than the ones processed in 'normal' developers, or is it just 'me and the myth'?

    - I do prefer the tonalities and the grain of Tri-X in Pyro-HD, but this is strictely a personal 'esthetic' appreciation! AND this is the closeest I can get to Agfapan processed in Rodinal, perhaps these were mythic too?

    PS. I am not praising nor disapproving any kind of process, just wondering and seeking answers.

    (*) 6x6 and 6x17 negs wet scanned on a V750 + SilverFast 8.
     
  19. michael_r

    michael_r Subscriber

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    Tanning is the hardening of the gelatin which purportedly increases sharpness by limiting the "migration" and/or clumping of silver grains. The stain is produced by development by-products (under the right conditions). Imagewise stain (as opposed to general stain) adds printing density so that the total density is metallic silver + stain. If there is significant imagewise stain, less silver is required to form sufficient density and contrast - which may further increase sharpness slightly, and reduces graininess slightly. In addition, the stain (dye) fills in some of the space between the developed silver grains, which can further reduce graininess slightly. That is what this thread was about - ie does the "grain masking" effect of imagewise stain have an offsetting effect on sharpness.

    Hope this helps.
     
  20. Ian Grant

    Ian Grant Subscriber

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    There's two types of stain produced one just by oxidation and the other caused by the development process, these shouldn't be confused. The old myth of puting the fixwed film back in the spent developer just adds general oxidasion stain which you don't want as it can be patchy.

    The Tanning and staing in the development process takes place at the same time.

    Ian
     
  21. Alan Johnson

    Alan Johnson Subscriber

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    IMO the perceived sharpness does not come from the acutance at the immediate edge of light/dark transitions but from adjacency effects ,often due to reduced agitation.I have attached scans of prints (high contast and dark to demonstrate the effect) from FX-2 (high perceived sharpness, large grain) and Pyrocat HD (lower perceived sharpness, small grain) form the same film.Sandy King, whose tests are probably more accurate than mine, did not find such a large difference in perceived sharpness between FX-2 and Pyrocat HD.
     

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  22. Gerald C Koch

    Gerald C Koch Member

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    The edge effect is certainly evident in the FX-2 example. The area just around the cross is noriceably lighter. Due to the nature of the subject it's hard to determine the relative sharpness between the two images. However if you look at the small lighter detail in the far lower right of both images the FX-2 images does appear to be sharper.
     
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  23. DREW WILEY

    DREW WILEY Member

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    Perceived sharpness (acutance) in the final print itself is generally superior with a tanning developer because of improved edge effect. This is readily detected just by normal viewing, and has nothing to do with mysticism or pyro wars. It's a simple fact a kid can spot who's too young to even read.
    It applies equally to all formats, given a comparable degree of typical enlargement from the same type film and same amt of development. Beyond this, there are way too many potential variables to give a pat answer, as well as atypical cases where you might not want these characteristics.
     
  24. michael_r

    michael_r Subscriber

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    The reason commonly given to explain the purportedly stronger edge effects with Pyro (note I'm speaking strictly of Pyro for now, not Cathechol) is that the tanned gelatin does not as readily allow the "escape" of bromide by-products. However again it seems to me there should also be an offsetting effect since the tanned gelatin should also limit the migration of developer and development by-products within the gelatin. In fact this is one of the features that is supposed to give Pyro a resolution advantage (less infectious development etc). So again it seems like writers such as Hutchings pick and choose the positive attributes.

    I've gone back to some texts regarging the Tanning/Staining issue and will post some notes here. Inconclusive as usual. There are apparently two "stages" of tanning etc. Some of it seems to come down to semantics. More to come.

    Appreciate all the feedback so far. Again I'm not for or against in any way. Just trying to flesh out a few things in the literature. PMK and WD2D+/H+ are fine developers in my experience - although they seem heavily film-dependent (for example I've found WD2D+ to work very well with FP4+ but give a massive speed loss with Delta). As for Pyrocat, I have never used it so I can't say anything about it or how it works.

    Regarding Alan's test - I'd like to know a little more about the methodology. Agitation etc.
     
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  25. DREW WILEY

    DREW WILEY Member

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    Tanning is only part of the equation. The other pertinent half is the image stain, which can be brownish, yellow-green, etc. By specific dev choice and mating it to an appropriate paper, quite a
    bit of control can be obtained, esp w/VC papers. Discussing all the potential nuances will in fact lead
    one into "pyro wars". A lot depends upon what you are trying to achieve. There are a lot of good
    pyrog. and pyrocat formulas out there right now, and a degree of experimentation with several of
    them will lead to answers a lot faster than tracing all the past quarrels. But specifics require a specific dev in question to begin with. The chemical effect really has nothing to do with "dye clouds"
    as in color photog.
     
  26. DREW WILEY

    DREW WILEY Member

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    I forgot to add ... there is in fact a lot of older literature on the nature of infectious development
    and tanning. Technicolor and dye transfer were both tanning dependent. It's quite a complex topic, actually.