Pyro Step Wedge

[Hans Berkhout]

I need a 31 step transmission step wedge that was processed in Pyro (PMK, Pyrocat HD). I'd appreciate detailed suggestions as to where/how to obtain this item.

I understand I may have to make one myself but why spend time reinventing the wheel?

Thanks in advance.

[Andrew O'Neill]

Contact print a step wedge onto your film of choice, develop in a staining developer, and presto, you've got what you wanted. But seriously, I don't ever recall seeing a commercially made pyro stained step wedge. Why do you need one?

[Michael R]

It would help if OP explained the goal. But yes, you'd have to make one, even if you're only looking for something generalized/illustrative. Assuming you want it to have any kind of meaningful application to your own work, the step wedge should be made using your own process, with the developer you use. Sensitometry with staining developers is tricky, so if the goal is to figure out how the negatives will print, you have to be specific with the process. For example, if you use PMK, a Pyrocat step wedge isn't going to be of great value. Etc. (you get the idea).

Hope this helps.

[Hans Berkhout]

Why? because I want to calibrate my dichro enlarger light source to print pyro negs with variable contrast paper. I have found Paul Butzi's calibration method very useful in this regard, with my D23 processed film.
See http://www.butzi.net/articles/vcce.htm

I could expose in camera but then I would have to cut my 31 step wedge in two pieces to fit a 4x5 holder- reluctant to do that (I'd fit a Expo Disc on camera lens and expose for zone IX).

Exposing under enlarger? I have no idea what EV to aim for, what exposure time, without running into reciprocity failure etc. I've done a few @ different exposure times and the resulting strips' higher or lower end don't always show separation. That's me reinventing the wheel. I'd probably get there. Eventually. Some precise advice would help speeding things up.

[Ken Lee]

Why not purchase a step wedge, make your own contact print(s) on a few sheets of film, then develop them in your chosen developer ?

[ic-racer]

You don't need or want a stained step wedge to calibrate you enlarger head.

"Calibrating" a color head involves calculating what extra color density on the head is needed so all contrast ranges print the same gray. The calibration pertains to your paper and enlarger head. The calibration has nothing to do with your negatives or stain. If the stain in your negatives alters your ISO-R value in a print don't worry, as the ISO-R values are a range anyway. Besides, who prints to a ISO-R value anyway. You will be adjusting you contrast as needed for each individual negative, if they have stain or not.

[Drew Wiley]

You have to have your step wedge matched to the specific film and type of pyro you have in mind anyway, since different formulas yield somewhat different colors
of stain. Ordinary step wedges can be purchased with all the steps on a single piece of 4x5 film. If you contemplate this as an interesting project for some reason
or another, go ahead. But you'll be doing a bunch of complicated stuff that is utterly redundant in terms of getting good VC prints from actual pyro negs. It's like
trying to assimilate an auto repair manual before you've even got a driver's license. You're making things WAY more complicated than they need to be.

[koraks]

I've only just started darkroom printing, so I don't know anything, really. All I can tell is that I personally can only see the point in calibrating my enlargers with a step wedge if I were to do a large number of prints from negatives that are exposed and developed to exactly the same contrast, on the same film, with the same developer and printed on the same size, on the same paper. That would eliminate the need to do test strips for each negative. But since I work with haphazardly exposed and developed, real-world negatives on a variety of films and developers, I guess I'm comfortably stuck in the stone age where no step wedge will ever be able to help me ;)

[Drew Wiley]

No, it wouldn't eliminate the need to do test strips. Every neg is a little different, and different brands of VC paper behave differently, even with minor changes in developer or even the specific mix of light color. And until you actually look at the final print, it's hard to judge what you need to do. Making test strips is super-easy anyway. Do yourself a favor and learn to work with just one film, developer, and paper first. Take your best guess and stick with that until you master the basics. Afterwards you can branch out. You're going about this backwards. Sure, there will be a few potholes along the road leading out of town. But that kind of thing has to be negotiated anyway. That's how you learn. If you enjoy the technical aspect to all this, that's fine too; but it can become a distraction that won't necessarily lead to better prints anytime soon. Just take it a step at a time and have fun.

[Andrew O'Neill]

Oh I see why... As Drew says, you're making it way more complicated than it needs to be. Just contact print the stepwedge you have under different settings for your dichroic head, and that'll tell you the contrast for that particular paper.

[Bill Burk]

Exposing under enlarger? I have no idea what EV to aim for, what exposure time, without running into reciprocity failure etc. I've done a few @ different exposure times and the resulting strips' higher or lower end don't always show separation. That's me reinventing the wheel. I'd probably get there. Eventually. Some precise advice would help speeding things up.

I was going to join the camp of "use the strip you got from Stouffer" but historically, Pyro was going to be considered the standard developer before D-76 became the standard... So there has to be value in having a Pyro developed master step wedge.

Hope you realized it... every step is a (a third stop ? in 31 step scales?) of exposure, you only need to adjust the time you tried... by counting the steps that show no detail... at least in the straight line section.

I always like to place the exposure so that two steps are completely clear on the negative, so that I can get good readings on the toe of the film. This is for a step wedge of the film's characteristic curve... not making a step wedge to use as a master step wedge.

So take your step wedge best effort and re-number in the opposite direction. You might not get all 31 steps... If some of your steps in the thinner densities measure exactly what you want, give them the numbers 1, 2, 3

For example step 20 might be 0.30, step 21 might be 0.20, step 22 might be 0.18 while step 23 is 0.10. So call 20 = 3, 21 = 2, "crossed out 22" and 23 = 1

[Peter De Smidt]

Follow Butzi's procedure with the Stouffer step wedge. Make your chart for your settings. Print.... I've used this system for many years with Xtol negs, PMK negs, Pyrocat negs..... There's no need to develop various step-wedge copies in different developers.

[Hans Berkhout]

Thank you all. Especialy Bill and Peter who read my question and gave it some thought, thanks your contributing your insights.

Pyro stain plays a role not only as density but also as a contrast reducing color mask, especially in the highlights ( G. Hutchings, The Book of Pyro). I am curious if Butzi's method would give me a different Y/M table when done with a pyro stained step wedge as compared to the -extremely useful-one I made years ago with a "silver only" Stouffer T3110 step wedge. Without exploring theories, pros, cons etc. I'm just going to experiment, try this and see if it will lead to something helpful for my printing of pyro stained negs on the VC paper of my choice.

[Peter De Smidt]

Since the pyro stain is proportional to density, you will get more of a contrast change in the bright areas of the print, as more of the blue light is filtered out. Consider two negatives of the same full range scene. The first negative is developed in a non-staining developer such that Zone VIII in the scene gives 1.3 above film base plus fog using the blue channel of a densitometer. The second film is developed in Pyrocat HD to the same density, again using the blue channel to measure density. With this negative the total Zone VIII density will be make up of about 30% stain and 70% silver density. If you print the negative using the same settings on the color head, there will be differences in contrast between the resulting prints, especially in the lighter areas. Does that matter, though, for the sake of printing? Suppose negative one prints best with a grade 2 settings on the color head. The best rendition of the high lights of the second negative might be better with grade 2.5 or 3. So just use that. Butzi's system gives an easy way of adding or subtracting contrast from the print while keeping near white elements in the print constant. Thus you determine exposure for the near white, using a test strip. Now make a print using your best guess filtration and the exposure just determined. Examine the print. If you need more or less contrast, consult the chart you made using Butzi's procedure, and adjust filtration to achieve the contrast you want. You can make this a complicated as you'd like, using different settings for various areas of the print....

[Doremus Scudder]

Thank you all. Especially Bill and Peter who read my question and gave it some thought, thanks your contributing your insights.

Pyro stain plays a role not only as density but also as a contrast reducing color mask, especially in the highlights ( G. Hutchings, The Book of Pyro). I am curious if Butzi's method would give me a different Y/M table when done with a pyro stained step wedge as compared to the -extremely useful-one I made years ago with a "silver only" Stouffer T3110 step wedge. Without exploring theories, pros, cons etc. I'm just going to experiment, try this and see if it will lead to something helpful for my printing of pyro stained negs on the VC paper of my choice.

Hans (and Peter and the rest of you who think that pyro stain is some kind of VC filter...)

Despite Gordon Hutchings stating this in his book, I've come to believe that it simply isn't true, and that PMK negs don't print radically differently on graded vs. VC papers.

Sure, the stain is "yellowish green," or brown, and must have a tiny bit of an absorption spectrum. The point is, is that this absorption is weak, and still passes a lot of blue. Once you start filtering, it is the color of the filter that predominates; the stain plays a minor role, if any.

Furthermore, if the stain does block blue light and pass more green, as many maintain, then using higher contrast filters should have a greater effect than with a similar contrast on a graded paper, since part of the blue is already blocked, and you're filtering out the green with the magenta filter thus filtering out two colors of light, the "stain" presumably adding some neutral density to the highlights... I've never experienced a PMK neg that printed well on graded paper needing a VC paper with markedly less contrast (often, the opposite is true).

And, calibrating a stained step wedge is going to be a bit tricky; blue channel only, blue+green, white? It might be interesting to see just how much the stain does (or doesn't) affect the transmission spectrum by making several exposures (as you would for a Zone Ruler) and then reading them through the different channels...

Take a look and Nicholas Linden's past posts dealing with this subject. He's the real authority.

Best,

Doremus

[Peter De Smidt]

Doremus, I'm fine with that. I haven't done any controlled tests to investigate this, although when I used PMK, many years ago, I did have issues with low highlight contrast. I didn't have a color densitometer back them. Perhaps the negs were simply not developed long enough. The upshot for this discussion, though, is that if Doremus is right, then there's even less reason to make a pyro step wedge.

[Cor]

Hans (and Peter and the rest of you who think that pyro stain is some kind of VC filter...)

Despite Gordon Hutchings stating this in his book, I've come to believe that it simply isn't true, and that PMK negs don't print radically differently on graded vs. VC papers.


Doremus

Doremus,

Much has been written on Pyro stain working as a VC filter and thus lowering the contrast by making the highlights well less white.. In my own experience I do see markedly different results between PyrocatHDC negatives printed on VC versus graded paper, BUT:

My mainstream VC paper (FB and RC) is Ilford, my graded paper is mostly Foma, Forte or Kentmere, and that also introduces a variable. I mainly use PyrocatHDC now for IR film: measuring for IR film (EFKE) is somewhat unpredictable, so I end up (some times) heavily overexposed highlights: IME if there is not too much stain, the stain nicely tames the highlights, but above a certain amount I cannot obtain a satisfactory print I switch to graded paper (or remove the stain).

I also use PyrocatHDc in stand development, I have not mastered that game (yet) and end up with quite a lot of stain, this negatives print better on graded paper as well.

it might very well be that when you have moderate stain the differences are minute.
Best,

Cor

[Drew Wiley]

There are so many possible variables that it gets damn difficult to forecast them, so I just go by specific test strips and experience, which makes things about a thousand times easier. But based on this experience, there is a minor discernable difference between a yellow-green PMK-ish stain effects versus a brownish pyrocat stain given an apples to apples VC paper application. This is logical. But the overall effect on contrast and highlight reproduction either way is analogous
to what happens with graded papers too. I'm not implying it would be identical, but it's not significant enough an issue to affect my workflow. When things can't
be managed normally, I resort to VC papers or masking or both (or nowadays, VC papers are largely norm, though I often use them as is they were ordinary
graded papers). Doing the research densitometry to plot the specifics is involved because you've got to read thru the stain, which is not something ordinary b&w
transmission desitometers do well. Read thru a deep blue filter like people sometimes suggest and you'll end up with so much total density that your machine can't do anything, really. So I just don't worry about it. Too much up-front prognosticating. Like I said, going about it backwards.

[Bill Burk]

The impact of stain color can be checked pretty simply: I think if you perform the Butzi calibration with Pyro-developed step wedge and Stouffer step wedge side by side on the same sheet(s) you will either see no "significant" difference, or maybe you'll see something subtle.

If there is a significant difference, or a subtle but measurable difference, then report back to us because the last time I saw a step wedge illustration there was just a slight difference in outcome...

[Hans Berkhout]

Makes sense Bill. I'll fine tune my process a bit, following the suggestions as given by you earlier. I should be able to produce a better pyro step wedge, suitable to use for the Butzi method. Which is to produce a table to turn my dichro head into a variable contrast with constant exposure light source, to be used for printing pyro negatives.

[Bill Burk]

Makes sense Bill. I'll fine tune my process a bit, following the suggestions as given by you earlier. I should be able to produce a better pyro step wedge, suitable to use for the Butzi method. Which is to produce a table to turn my dichro head into a variable contrast with constant exposure light source, to be used for printing pyro negatives.

I don't think you need to make another test strip. You could just measure the Pyro step wedge you got and write the density readings on it (india ink or an artists black ink pen like Faber Castell Pitt). All the information you need for comparison can be done by looking at Stouffer patches with the same or close densities.

If my guess is right, from what has been said so far, the significant differences you will see on paper will be in the straight line portion, right in the middle of the scale (for example somewhere in the range of densities from 0.5 to 1.5 where the highlights fall).

[Doremus Scudder]

Just a few more thoughts related to this topic.

First, as Drew and I have mentioned, calibrating a pyro step wedge is going to be difficult since you will not be reading neutral density from a silver image, but densities from both the silver and the stained image. The stained image has a non-neutral transmission density, and figuring out how that is going to affect specific papers is complicated process, which would involve plotting transmission spectra for different densities of your pyro negs, spectral sensitivity of your paper(s), etc., etc.

To expand a bit about pyro stain acting as a VC filter: The stain on a pyro neg may indeed change spectral transmission of different densities somewhat, but the effect of this is not always to "tame the highlights." If (and this is a big if) a denser area of a pyro negative blocks more blue light and transmits more green light to a VC paper than a less-dense area using white light, then this would have an effect on the overall curve shape of the paper. This would, however, be ameliorated somewhat by adjusting developing time in initial testing. However, this effect would only be optimized when using white light as an enlarging source (i.e., equal amounts of blue and green light as far as the paper was concerned). When we start adding filtration to this "package," things change a bit.

Thought experiment: Let's take a hypothetical pyro neg that has two density areas, one very dense and ostensibly with lots of blue-blocking stain (we're assuming for now this is true), and one much less-dense area, which has so little image stain as to block a small fraction of the blue light passing through it. We could practically consider it to transmit white light with almost no absorption. Let's print this negative on a VC paper using a white light source (no filtration); we get densities on the paper we can measure, say X for the thin area and Y for the dense area. Now, what happens to the relationship between X and Y when we start adding magenta filtration (or higher contrast filters) in order to increase contrast? The thin X density area will react to filtration neutrally, i.e., transmit the mix of blue and green light determined by the filtration. The dense Y area, however, since it has a lot of blue-blocking stain, will not. When white light is passing through the Y area, some blue light is being removed by the stain already, but lots of green is passing through. As we remove green with magenta filtration or the like, we end up with both green and blue being removed from the original white light; green by the magenta filtration and blue by the stain "filter." This would result in proportionally less light reaching the paper through the Y-density area as through the X-density area. Given that this light would also be bluer due to the magenta filtration, there should be a double increase of contrast: the increase of contrast caused by the magenta filtration, i.e., by removing some or all of the green component of the white light, AND the fact that proportionally less light in total is being transmitted through the stained area of the negative, giving more effective density to the Y area under blue(r) light than white light.

Stay with me here: This would mean that increasing magenta filtration (or changing to successively higher contrast filters) with a pyro-stained neg should result in a proportionally greater increase of contrast with a given amount of magenta filtration (or a given higher-contrast filter) when compared to a non-stained negative, in which the density consists entirely of silver and which is color-neutral. The increase in contrast would be proportional to the stain. The opposite would then be true when using yellow filtration or a lower-contrast filter when compared to white light: the decrease in contrast should be proportionally greater for the pyro-stained negative than the silver-image-only negative, and in proportion to the amount stain.

Now for the kicker: I have not found this to be true. Adding magenta filtration to pyro-stained negatives doesn't seem to result in such a proportional increase in contrast, at least not one that I notice. Mind you, I've not done exhaustive testing here, there may indeed be a contrast change due to the stain. However, in practical terms, it must not be very much. To really quantify this, one would only need a couple of (calibrated) negatives, one stained, one unstained, with two densities each on them that render the same reflection densities on VC paper when exposed under white light. One could then add varying amounts of magenta and yellow filtration and see if there were proportional changes. In the case of adding magenta filtration, the stained neg should increase in contrast with increasing magenta filtration faster than the non-stained counterpart until the maximum contrast of the paper is reached. I don't think this will be the case, since then there would be no contrast change for the stained negative at the extremes of magenta filtration. I've not found this to be the case. I get gradual contrast changes with pyro negs all the way up to maximum magenta filtration, which should not be the case if the stain is really blocking a significant portion of the blue light.

Since I'm in the process of building a new darkroom, I don't have access to facilities or equipment to test my hunch/hypothesis one way or the other at this time. Based on past experience, however, I really don't believe that pyro stain has a substantial effect on overall print contrast.

Hans, since you're planning on making a pyro step-wedge, maybe you will be in a position to confirm or disprove this. I'd be very interested in seering some hard data. I imagine that reflection density readings from the paper would be the way to go, and that the transmission densities of pyro-stained negs would be cumbersome to deal with.

Best,

Doremus