PMK Pyro and "Modern" Emulsions

[Drew Wiley]

Jay - the expression "modern" is relative. Films like HP5 and possibly Tri-X (and certainly the old-style Fortepans) stain more aggessively than the "thinner" T-grain and tabular grained emulsions. I think most of us would classify the late great Super-XX as a an-school film. FP4 is also a bit more aggressive in its staining characteristics
than say ACROS, which is about the same effective speed in PMK.

[Jay DeFehr]

Drew,

Have you tested your assertions? I have, and my results have convinced me that all "modern" (meaning films I've been able to test) films stain about the same, whether they're CCGT films or not. For a given silver density, a given staining developer will produce a given stain density within narrow margins among a wide variety of films. I think SXX was indeed a thick emulsion film, unlike HP5+, TX, FP4+, etc., which are all modern thin emulsion films. I have used a lot of Fortepan 200 and still have a lot of it in my freezer, and if it is in fact a thick emulsion film, it still conforms closely to the silver:stain ratios of modern thin emulsion films. I think the notion that some films stain better/more than others is a popular myth based on anecdotal claims made by people who have never measured the stain densities of their negatives or compared them to others. I've read thousands of stained step wedges, and seen very little variation in silver density : stain density among them. The differences I have seen are attributable to differences in developer formulation, not in the film stocks. The best staining developers produce near the maximum stain:silver density ratios, and near zero general stain. The rest fall short in one way, or the other, or in both ways.

[Drew Wiley]

I'm not guessing, Jay. Do this all the time, and have worked with just about all the sheet films out there except Tri-X, and many roll films too. And yes, at the moment
I still have some Forte 200 in my 8x10 holders. The end result can also be tweaked by
how long an alkaline afterbath is used - a nice feature with thin-emulsion films which
don't tend to stain as much. HP5 is a little more amenable to some of the old tricks
like Super-XX was used for, so although it might not be classified a thick-emulsion film in relation to certain long-discontinued items, it behaves that way relative to the other
current film options. Got the densitometer right next to the light box.

[Jay DeFehr]

Drew,

I'm interested to know how you've conducted your testing to come to such a different conclusion than I have. I expose the film I'm testing in a sensitometer and then process them, and read the resulting step wedges with a color densitometer, comparing the readings from the different filters to calculate the difference between silver density and stain density. Whenever I compare different films at a common silver density, the stain densities fall within the margins of accuracy of my equipment and process. I've never seen any data that suggests one film produces more stain relative to a given silver density than another film processed as close to identically as I can manage. Could you provide some of your comparison data?

I've worked with HP5+, and I've never found it to differ from any other film in its class regarding its processing behavior. The "tricks" most people associate with thick emulsion films are things like 2-bath development and water bath development, and I've not found HP5+ to behave differently in these processes than other films do.

The "after bath" is another notion I've been persuaded by my own testing is completely useless, and most often harmful, adding only general stain which functions exactly like fog with graded papers, and like fog with a low contrast filter effect with VC papers. I don't know a single formulator of staining developers who recommends the practice, and I'm not surprised by that.

I'm not saying you're wrong, Drew, I'm just saying it would take a lot of credible data to convince me I am.

[Drew Wiley]

Hi Jay - I don't get any fog from afterbath. I use it selectively (tray processing of sheets, manual drum for small format). Helps improves the highlight characteristics of
films which don't stain as readily - a little longer afterbath vs a shorter one (or none).
Films like 100TMax, ACROS, Pan F, Delta100, etc are generally improved by a longer
alkaline afterbath. FP4 and HP5 require more caution or the highlight stain will become
excessive on long-scale subjects. I weigh this factor in relation to the same PMK developer. Only with HP5 or Pan F do I tweak the standard PMK mix ratios. I could give
you some FBF reading, though I can't get to the dkrm tonite. It's always much higher
with HP5 (somewhere around .15), even worse with the old Fortepan 400 dual-coated
emulsion, which I never liked anyway. With these "relatively thick" emulsions, you get
a little more infectious perimeter (surge) development than with tabular grain films.
Staining also must inevitably be related to the type of polyester or acetate used in
various film mfg, though this is a bit more difficult variable to isolate with casual lab
readings. PMK is my standard developer for general photography (vs special lab use),
so I feel extremely confident about my statements. Use it and print form it almost every week.

[Jay DeFehr]

Drew,

I hope you won't be offended if I don't share your confidence in your statements. To know how much stain is being produced, one must subtract the silver density from the total density, or silver + stain density. A FB+fog reading alone doesn't tell one anything about the contribution of stain to the reading.

Regarding the after bath, I don't know what you mean when you say:

Helps improves the highlight characteristics of
films which don't stain as readily

In what ways does it improve? And what do you mean by:

FP4 and HP5 require more caution or the highlight stain will become
excessive on long-scale subjects.

Do you mean that the contrast can be too high? I've never seen any evidence that an after bath increases contrast.

Staining also must inevitably be related to the type of polyester or acetate used in
various film mfg

Not only do I believe the above to be untrue, I can't imagine any way it could possibly be true. The support doesn't stain, the emulsion does, by a process of polymerization. If you don't believe me, strip the emulsion off of a length of film support with some chlorine bleach, and then dunk it in PMK. No emulsion, no stain.

It is possible to be mistaken about all of these things and still get good results, which is why anecdotal evidence is worth so little in the absence of sound theory, and better still, empirical data.

[Drew Wiley]

Jay - highlight characteristics, i.e., reproduction characteristic in typcial silver printing.
The whole point of the stain is to modify the printing characteristics, therefore being
able to control the amount of this stain using an afterbath, and being able to improve
the amount of stain in films which otherwise stain weakly. Pretty simple concept...
Next, by "film base" you are technically correct. I was shorthand referring to it in the
sense of base plus unexposed emulsion (borders or otherwise unexposed fresh film).
Certain combinations of plastic plus sensitized gelatin which differ from product to
product. Generally, a film which is amenable to water-bath or other old-fashioned
"thick emulsion" effects will react in a manner producing more "tanning", although this
is not a fixed rule, just a practical observation. Pyro tans. We not only rely on this with
respect to PMK, but in technicolor film base, dye transfer and wash-off relief printing,
and several technical medical applications. The tendency of FP4 and HP5 to blow out
the highlights with too much staining has been discussed on other threads. You don't
need to believe if you don't want to. I need to believe it, otherwise my prints suffer,
or need a supplementary contrast mask to tame. Had a lot of experience with this.

[Jay DeFehr]

Drew,

You seem to be suggesting that the after bath increases stain formation in the highlights, with which I don't disagree, but I'd add that it increases stain density non-preferentially, throughout the entire density range of the negtative, adding neutral density, not contrast. VC papers react differently than graded ones do, and in that case the stain also imparts a yellow filter effect which acts to decrease print contrast.

Pyro does indeed tan, and a thick emulsion can potentially show more relief than a thin one. No argument there.

If HP5+ and/or FP4+ have any tendency towards blown highlights with staining developers, it is simply a matter of over development, not over staining. Stain is proportional to silver density and a function of the degree of development. If there is too much contrast, the film has been overdeveloped. A family of curves will illustrate the range of contrast a film/developer combination can produce given various degrees of development. If you overdevelop your film, it's not the fault of the developer.

[Drew Wiley]

Yes and no. Depending. One thing I like to do with Hp5 is plus develop in order
to maximize mackie line effect and midtone expansion. With this film, PMK allows
this while keeping overall granularity visually supressed, the well-known "watercolor" effect. Since Hp5 has a pretty distinct toe, on brightly-lit subjects, the
shadows need quite a bit of exposure, hence the highlight tend to block up. Just a
variable contrast split-printing technique is insufficient to rescue the highlight, though pyro makes them retrievable using a supplementary film mask. (Generally
I prefer straight-line films like the 200's or now 400TMY, which are easier to print).
But I did conjure up a pyro tweak for HP5 which wonderfully prints off the stain only, with no visible silver image! Just blue light vs stain, but this works only with HP5,
so this tells me there's something unique about this emulsion. Too bad Super XX isn't
still around to make a comparison. But I'm beginning to suspect that HP5plus has
undergone subtle reformulation in recent years that we're not informed of. And I have no idea if there's any truth to rumors of developer-incorporation in certain
Ilford films.

[Kirk Keyes]

Drew - what do you use for the afterbath - the spent developer or some other solution?