The effect of pyro stain on VC paper contrast.

An experiment was performed to see if pyro stain had any effect on the intrinsic contrast of VC paper.

The experimental method

A 4x5 sheet of Plus-X was given a uniform Zone VIII highlight exposure and developed for 12 minutes in PMK developer.

The silver was removed with P. Ferricyanide and Thiosulfate bleach.

The resulting stained negative was put in a condenser enlarger and grey-strip prints were made with #1, # 3 1/2 and #5 contrast filters. Exposure times were the same for all strips and ranged from 1 to 64 seconds. The aperture was adjusted so the tones would line up with grey-strip prints made without a pyro-stain negative.

The experimental results



In each pair of strips, the top one was made without the pyro-stain negative, the bottom with. The exposure shown is as measured with the DA exposure system.

Obviously, with the pyro-stain negative/filter in place extra exposure needed to be given to compensate for the pyro stain. What is very interesting is that increasing amounts of extra exposure need to be given as the contrast grade of the VC filter increases.

Grade 1 was given 0.4 stops more exposre
Grade 3 1/2 was given 0.7 stops more
Grade 5 was given 0.8 stops more

Conclusions

Pyro stain does not have any appreciable effect on VC paper contrast. There are slight variations in the match-up between the tones but they are in line with the variability of this type of experiment: tray processing, aging developer, room temperature for temperature control, forgetting to set the timer for print development and guessing when it's time to pull the print ... but these are the normal variables encountered in any darkroom.

The effect of pyro stain is to add simple density, the amount of density added by a given amount of stain changes with contrast filtration.

A pyro negative will gain contrast faster than a conventional negative when the contrast filtration is increased. If a conventional and a pyro negative produce identical prints at VC filtration #2 then the pyro negative will produce a higher contrast print at VC filtration #5. The reason being that the stain is seen as a higher density with higher contrast filtration and stain is proportional to silver (mostly).

All developers produce negatives with different HD curves. Even if pyro and a normal negative are development adjusted for identical ‘CI’s [begging the question of defining CI for a pyro negative] the look of a print from the pyro negative may not be the same as the look of a print from the normal negative. Other effects, such as grain masking and image softening due to diffuse stain and image sharpening due to tanning, will also effect the look of a print made from a pyro negative.

But, whatever the effects of pyro stain, differentially lowering paper contrast in the highlights isn't one of them. If pyro stain had an effect on paper contrast the grey patch strips shown above would not match for contrast.

* * *

It is possible the results may be different with other films, developers and light sources. This experiment is very easy to make for oneself - it takes only the odd bits of an evening. If you doubt the results, please try the experiment for yourself and post your outcome.

Thanks for doing that! I use PMK and am glad to have that cleared up. It is harder for me to visually estimate contrast by eyeballing the PMK negative compared to xtol/d76, but at least the contrast will work the same.

So, pyro stain does not differentially effect highlights. Are you also saying that it does not effect overall contrast as well?

Unless I misunderstand, I would have to disagree in the top two examples. The density difference on the right is about 1.0 (I cannot clearly read the numbers but visually it looks like you have lost one step)

Based on the color of pyro stain, it should affect the image contrast differently across the filter gamut. That is what I see for #1 and 2, but not for the remainder. This is reasonable for having an effect at one filter value but not at all.

PE

John, his test does not test negative highlight handling or negative highlight range handling. Uniform negative exposure was used to eliminate that variable, so that only paper contrast was being tested. Zone VIII will be fairly light, meaning a dark thoroughly stained negative that should show off any VC print differences better than a dark zone that would be thin on the negative.

jp498 said:

John, his test does not test negative highlight handling or negative highlight range handling. Uniform negative exposure was used to eliminate that variable, so that only paper contrast was being tested.

Click to expand...

Exactly. It isn't a comprehensive statement about highlights and pyro. It just seems to show that whatever effect pyro has, it isn't the color of the stain affecting the HD curve of the paper to any significant manner.

I was rather taken aback at the lack of affect.

I'll scan the strips with a densitometer and add the density numbers to the picture above - won't happen until tomorrow evening. The earlier set (not shown here) - before tweaking the exposure so the tones align - showed HD curves that were darn near identical.

In the meantime here are the HD curves of the earlier set - I was looking at the highlight sections of the curves as that was where differences were expected. You can see the constant horizontal offset between the curves with and without the filtration. As an example: if you look at the two red curves and go horizontally between them there are always 5 divisions (0.5 stops) separating the two curves.

John Bond said:

Are you also saying that it does not effect overall contrast as well?

Click to expand...

No, of course not. The stain is part of the density so it is also part of the contrast.

Photo Engineer said:

I would have to disagree in the top two examples. The density difference on the right is about 1.0

Click to expand...

Sorry, I don't understand this.

The scan shows 3 pairs gray-strips.

The top pair of strips are at grade #5, the middle at #3 1/2 and the bottom at #1.

Within each pair the top strip shows the tones without a pyro stain in place and the bottom with a pyro stain.

The numbers on each patch indicate the amount of exposure given before filtration, they have nothing to do with density.

Comparison is presented as purely visual: is the difference visually significant?

There are, of course, minor variations in tone. Expose a sheet of paper with uniform light (a problem in its own right), develop it and measure density across its surface and there will be minor variations. If there were no minor variations I would suspect the experiment of being fudged.

I'm not a person to test, but I use graded papers, and negs that have been developed in Pyrocat have more contrast than conventionally processed negs. That is why I like Pyrocat, because I can get good contrast on negs that would otherwise be considered a little thin. Not very scientific, but that's my 2c worth

Nicholas,

Your test is similar to the test I suggested on the original thread on this topic.

At any rate, I see some problems with your interpretation of your results.

A thought experiment:

First, assume that a pyro stain acts to remove some blue light (i.e., as a yellow filter). Let's assign it an arbitrary value, say as a "Grade 1 Filter". Lets call our pyro stain filter P1. A regular #1 filter we shall designate G1.

If that is our starting point, it is easy to see that:

1) using a regular grade 1 filter (G1) plus our pyro P1 filter together will have no effect on VC paper contrast (no more than stacking a pair of identical filters over a camera lens). and that...

2) We can see that, as you move to a more magenta filter, which as far as the paper is concerned, passes blue light much more than other wavelengths, that adding the P1 filter, which subtracts blue light in the path, will add neutral density in exactly the same way as using a regular grade 1 filter together with, say, a number 5 filter would. This, however, would not affect contrast.

Your results are consistent with the above scenario.

However, this test does not determine if the pyro stain filter has any effect on overall paper contrast at all, since filtered light is being used to make the prints. If the pyro stain does correspond to some degree of VC filtration, which your results tend to suggest, then it will have some effect on overall contrast, just as a regular VC filter would.

Now, a pyro negative has a proportional stain. This means that, if indeed the P1 filter corresponds to a G1 filter, that, when using white light, you would be altering the mix of blue/green light balance that passes through a negative and reaches the paper in proportion to the stain. Also, if you used a G1 filter together with the pyro neg, you would be "evening out" the proportionality present in the pyro neg. Conversely, if you used a magenta filter, you would build neutral density in the areas of higher stain in proportion to the removal of blue light, while not doing this in the less dense areas of the negative, which have little stain, thus increasing contrast overall. This all in comparison to an "ideal" negative that had no pyro stain.

All this still needs to be tested before one can conclude that the pyro stain has no effect on the contrast. For me, I find in logical that if one selectively filtered the highlights of a print with a G1 filter while using white light as a light source, that the filtered parts would receive less blue light, and therefore, may be of "less contrast," depending, of course, on what role the added density of the filter plays as a neutral density filter with this particular spectral mix (whether or not this filter is a pyro stain or a normal VC filter).

I've been thinking a bit about possible ways to accomplish this. Maybe you could comment on the following scenario. Assumed are developing times with the films and developers used that yield "normal" negatives.


Make identical negatives of a step wedge.

Develop one negative in a non-staining developer (Neg 1)

Develop the other in a staining developer

Bleach the silver from the pyro stained negative to get a progressive pyro-stain mask. (Step Mask)

Print the step-wedge negative (neg 1) with and without the step mask. When printing with the mask, the mask should be aligned so that less-dense areas of the mask correspond to less-dense areas of the negative. The ideal alignment may need tuning in order to really correspond to the way the stain forms in a real pyro neg, i.e., which stain density really goes with which silver density, but even errors here should still deliver usable results.

Printing time or aperture need to be adjusted so that one of the lower-density steps, say one corresponding to Zone II or III, always prints at the same print density. The difference in the other steps will tell if there is, indeed, any proportional pyro-stain effect.

Make sure to use white light as one of the light sources in the test regime.

I might suggest:

White light
00 filter
2 filter
5 filter

as a starting point.

In this regime, you use the same film, paper, print developer, enlarger/light source etc. Most variables are eliminated, which should make observing any effect of the pyro stain easier.

If the pyro stain does have an effect, one would expect the following results:

1. The white light prints should show different highlight densities, with the pyro-mask print highlights having less density.

2. The #00 filter prints should show no difference, the stronger 00 filter prevailing and effectively overriding the pyro stain.

3. The prints made with the #5 filter should show increased highlight density in the pyro-mask print due to the neutral-density effect of the stain.

4. The entire range of difference should point to a place where the effect of the pyro stain is equal to a particular VC filter. In other words, there should be a place where the contrast curves cross. This may be close to the #2 filter prints.

I'm really interested in your analysis of the above.

Best,

Doremus Scudder
www.DoremusScudder.com

Doremus Scudder said:

I'm really interested in your analysis of the above.

Best,

Doremus Scudder
www.DoremusScudder.com

Click to expand...

Thanks Doremus, a good overview which I'd 100% agree with.

As a user of staining developers I think the effects of the staining is subtle, and something that's overlooked is how films stain quite different colours, some almost neutral, others yellow-brown or reddish. So choice of film & developer has a greater effect with some compared to others. Forte Pan 200 gives the most marked yellow staining of any film I've processed in Pyrocat.

Ian

The top two examples (1 and 3-1/2 filters) do show significantly less contrast for the pyro stained negative, but nothing that can't be handled easily. Visually, the gradation seems somewhat more even with the pyro stain.

Not all that is yellow is a contrast filter

Doremus Scudder said:

If the pyro stain does correspond to some degree of VC filtration ....

Click to expand...

Here we come to the elephant in the room.

The evidence above is that pyro stain does not correspond to VC filtration. It seems its pass-band is wrong for effecting contrast. It's not the right color.

Here is an image of Kodak polycontrast filters for #2, 0 and -1. The fourth filter is the pyro-stain negative used in the experiment.



The pyro stain, though 'yellow', is the yellow of a #2 VC filter. A #2 filter does not change the contrast of VC paper - it merely adds one stop of density, about the same as the pyro stain negative. The color of a #2 filter and pyro stain are about the same orange color as an OC safelight filter. VC filters pass non-actinic light - allowing more light to see by when dodging and burning; Ilford's #2 filter is light pink, passing red light while attenuating yellow through blue; Kodak's is more sophisticated, passing red and yellow to see by while attenuating blue and green and is thus orange in coloration.

Pyro stain, it seems, blocks both actinic green and blue - making it ineffective as a contrast filter.

Other pyro developers produce other colors of stain - they may affect contrast. But I think the onus now is to prove that they do - argument is futile: http://www.youtube.com/watch?v=kQFKtI6gn9Y&feature=related

My own observations, and I admit not a rigorous scientific test, is that film normally developed in nonstaining developer prints more or less similarly on graded paper and VC paper without filtration. Film developed with pryogallol that prints normally with graded paper (similar to film developed with nonstaining developer) will require a significant amount of magenta filtration to achieve a similar contrast as on the graded paper.

If the color of the stain is not acting like a yellow filter, is there some other explanation of my observations or am I misinterpreting what I think I am seeing.

It's an issue chasing it's own tail.

I'm currently reading an article on Pyro devs that in one section pretty much sums up Sandy King's reasoning behind Pyrocat HD and I'd guess PMK. The article aptly called Pyro Yesterday & Today was published in the British Journal of Photography in 1949.

Pyro negatives print with finer grain than would be expected which is mentioned in the article, Kodak differentiate between Print Grain Index and the Film grain, and this is important with Pyro negatives because the staining is in the gelatin surrounding the film grain.

One of the arguments against the Pyro negatives and VC/MG papers combination is that some claim they don't give a full range of contrasts, which is not my experience, however I never print much outside Gd 2 - 3.5.

I think the problem with this particular experiment is it's mimicking placing a VC filter (say Gd2) permanently in an enlarger then negating that with filtration to get other grades, and the results show that to be the case.

So thinking laterally assuming max stain is equivalent to Gd 2 in the highlights then that drops proportionally to the shadows where there's no stain.

Ian

Nicholas Lindan said:

An experiment was performed to see if pyro stain had any effect on the intrinsic contrast of VC paper.

The effect of pyro stain is to add simple density, the amount of density added by a given amount of stain changes with contrast filtration.

A pyro negative will gain contrast faster than a conventional negative when the contrast filtration is increased. If a conventional and a pyro negative produce identical prints at VC filtration #2 then the pyro negative will produce a higher contrast print at VC filtration #5. The reason being that the stain is seen as a higher density with higher contrast filtration and stain is proportional to silver (mostly).
.

Click to expand...

The experimental setup is to test for density differences. And that is what you find and in agreement with our experience. And I use this in the darkroom practice, when I print on VC paper from pyro-negatives.

Jed

Nicholas;

After seeing the curves and rethinking the issue, I have to agree with you and disagree with myself.

Thanks for posting the curves.

PE

Nicholas Lindan said:

Here we come to the elephant in the room.

The evidence above is that pyro stain does not correspond to VC filtration. It seems its pass-band is wrong for effecting contrast. It's not the right color.

Here is an image of Kodak polycontrast filters for #2, 0 and -1. The fourth filter is the pyro-stain negative used in the experiment.

The pyro stain, though 'yellow' is really the yellow of a #2 VC filter. A #2 filter does not change the contrast of VC paper - it merely adds one stop of density, about the same as the pyro stain negative. The color of a #2 filter and pyro stain are about the same orange color as an OC safelight filter.


Other pyro developers produce other colors of stain - they may affect contrast. But I think the onus now is to prove that they do - argument is futile: http://www.youtube.com/watch?v=kQFKtI6gn9Y&feature=related

Click to expand...

Fantastic work. I'll buy you a beer next time we are together!

Nicholas,

I agree, the task is to somehow prove that the pyro stain is indeed working like a VC filter, or not. Arguing about it is certainly not a profitable course of action. Brainstorming about devising/improving tests, however, does seem so, and fun as well

Here are some random thoughts on the subject.

The premises to be tested (as I see them) are a) that the pyro stain acts to block blue light like a lower-contrast VC filter and b) that such a filter, when applied proportionally to the silver density in a negative, acts to change the contrast on photo papers in the areas where greater stain density is present. Furthermore, it is theorized that the effect, which amounts to increasingly less blue light making it through the progressively denser areas of stain, affect VC and graded papers differently, decreasing contrast in the former and increasing it in the latter. Designing tests for this is the challenge. I think the regime I suggested earlier will do the job, but the subject is rather complicated and it is easy to overlook an aspect of it. Any feedback/observations on my suggestion would be appreciated.

The #2 filter you show must be more than a ND filter. Otherwise it would not have a color, but appear neutral gray. It may pass a similar percentage of blue vs. green light as found in most enlarger light sources, making it similar to the enlarger light source in its contrast rendering on VC paper, but I doubt it is just ND. I believe it would behave very differently with different light sources than an ND filter. There must be spectral info on VC filters available to check this somewhere, but, after Googling for a while, I don't seem to be able to come up with anything.

What test would be needed with a pyro-stain mask to see what its pass band is? I imagine fairly sophisticated spectral analysis equipment would be needed. Maybe someone has access? The thing to do would be to compare the pyro-mask pass band with those for VC filters. And then there is the question of the color of the pyro stain, which is dependent on many factors. It could be that some stains behave very differently than others.

The main reservation I have with your test is that it uses an overall pyro-stain mask of a single density. I don't see how a "with and without overall pyro stain" test will give any usable results when only tested with VC filters in place along with the pyro mask. The problem as I see it is that (assuming that the pyro mask is functioning as a yellow filter) any filter equal to or "stronger" than the pyro mask will simply override it. E.g., if the pyro mask equals a #1 filter, using a #1 or less contrasty filter will just give the same result as using the filter without the mask as far as contrast is concerned.

Furthermore, using a mask with just one density together with higher contrast filters (again, assuming the stain functions as a VC filter) will just add neutral density overall the stronger the filter gets. (the result you got, by the way, which makes me surmise that the pyro stain may be acting at least a bit like a blue-blocking filter). The proportionality of a pyro-stained negative is not in the mix here and not being tested (more later).

White light (i.e., unfiltered enlarger light) should be used and the contrast with the pyro stain mask compared to prints made with different VC filters. A straight white-light print should be made as well. Then it should be able to be seen which VC filter is most closely approximated by the pyro stain. Unfortunately, if, say, the number 2 filter and the pyro stain mask and white-light print all match up, that only tells us that the pyro stain and the #2 filter are passing blue and green components in the same proportion as the white light, not that anything gets blocked at all...

So, then, one would have to see if the pyro mask added the same or similar amount of neutral density when stacked with different magenta filters as the #2 filter did. If so, then one could assume that its pass band, at least as far as the light the paper sees, is similar enough to a #2 filter to work as such.

Now, back to the real issue, which is the proportional stain. The test I suggested would show the effect of proportional staining on contrast if there is any. An alternate test might be to use the pyro mask you have already, make a prints of a step wedge without the mask and then with the mask covering only the more dense half of the step wedge. You should be able to make these at the same exposure. If there is then a difference in the contrast or progression of the denser wedges (i.e., in the less-dense area of the print), then one would have some rough evidence that proportional staining would have an effect on contrast rendering.

I kind of think that unless we have white-light prints to compare to, and use a regime where higher negative/step wedge densities are coupled with more stain than lower ones, we are simply barking up the wrong tree by not testing what needs to be tested.

I am not in a position to do any testing at the moment, being away from my darkroom until the summer... I am, therefore, grateful to you (and others) for taking the time to test and present what you have done here. It is a fascinating and thought-provoking subject, and I'm enjoying thinking about it. I'm really hoping that you or some other intrepid and generous soul here will continue the testing.

Thanks and best,

Doremus Scudder

www.DoremusScudder.com

I would think that the number two filter would be designed to block both blue and green equally -- thus not affecting the native contrast of the paper (contrast it would give without a filter used) yet keeping the exposure the same as using filters numerically below and above it.

PS...I always felt it was the #2.5 that tended to be more contrast-neutral. Not scientifically tested, though, by me.

PS #2...one could assume that not all papers have equal proportional response to blue and green light, thus different papers might have a different filter that is contrast neutral. This could explain why it is better to have the range of filters instead of having just a colorless neutral density filter in the middle of the range. I suppose the type of light source and the spectrum it puts out could affect the relative response of the paper to blue and green light -- thus changing which filter is actually contrast neutral.

Vaughn said:

I would think that the number two filter would be designed to block both blue and green equally -- thus not affecting the native contrast of the paper (contrast it would give without a filter used) yet keeping the exposure the same as using filters numerically below and above it.

Click to expand...

Exactly what it does, block blue and green but pass red and yellow: yellow-orange.

Vaughn said:

I always felt it was the #2.5 that tended to be more contrast-neutral. Not scientifically tested, though, by me.

Click to expand...

Same here. When I print negatives [for enjoyment, grey strips aren't enjoyment] it's #2.5 that I reach for if I want 'normal' contrast. #2.5 also has a smoother HD curve than #2, which is still somewhat bumpy.

Thanks Nicholas, I am out of my league here and was writing more to get the idea in my head better than just reading.

Ian Grant said:

It's an issue chasing it's own tail.

I'm currently reading an article on Pyro devs that in one section pretty much sums up Sandy King's reasoning behind Pyrocat HD and I'd guess PMK. The article aptly called Pyro Yesterday & Today was published in the British Journal of Photography in 1949.

Pyro negatives print with finer grain than would be expected which is mentioned in the article, Kodak differentiate between Print Grain Index and the Film grain, and this is important with Pyro negatives because the staining is in the gelatin surrounding the film grain.

One of the arguments against the Pyro negatives and VC/MG papers combination is that some claim they don't give a full range of contrasts, which is not my experience, however I never print much outside Gd 2 - 3.5.

I think the problem with this particular experiment is it's mimicking placing a VC filter (say Gd2) permanently in an enlarger then negating that with filtration to get other grades, and the results show that to be the case.

So thinking laterally assuming max stain is equivalent to Gd 2 in the highlights then that drops proportionally to the shadows where there's no stain.

Ian

Click to expand...

My photography carreer started in 1947. At that time the pyrogallol developers behaved differently. The grain was unacceptable for 35 mm enlargements. By now, this has changed. The modern films have different properties. The grain with modern film is more obscured by the stain. The stain, and its optical properties have changed.

Jed

There would be some merit in comparing the maximum and minimum (base) stain for a variety of films and 2 or 3 staining developers.

One of the reasons why perhaps the debate (in the past) is like a cat chasing it's tail is there's too many variables, to truly show what's really happening first it's necessary to find a developer/film combination that exhibits a high level of staining, by that I really mean a marked colour shift as well.

Otherwise it's a lot of testing to just give inconclusive results. Nicholas has given a good base point in these tests for Plus-X in PMK, it's not a film or developer I use but I don't think the stain is as strong as some films I develop in Pyrocat and PMK will give a different stain. As I said before some films have no noticeable staining at first glance in Pyrocat others quite marked.

I sit in the middle using a staining developer with no issues with a variety of films, great tonal range, excellent sharpness and very fine grain, and all negatives prints well with VC/MG papers.

However others repeatedly suggest they have issues with staining developers and VC/MG papers and knowing how pronounced the stain colour can be it must have an impact in some cases and so to begin with an extreme is the best place to start.

Throwing another spoke in the wheel a similar test should be carried out with a non staining developer, many common film developers can impart a some stain.

Ian

Jed Freudenthal said:

My photography carreer started in 1947. At that time the pyrogallol developers behaved differently. The grain was unacceptable for 35 mm enlargements. By now, this has changed. The modern films have different properties. The grain with modern film is more obscured by the stain. The stain, and its optical properties have changed.

Jed

Click to expand...

It might surprise you that by the late 1930's pyro devs, often Pyrocatechin rather than Pyrogallol but still staining developers were being used to give high quality results with 35mm films. The article I'm reading is a sequel to an earlier 1939 article by the same author and he's describing using very dilute Pyrogallol developers with 35mm films

However his approach was not the norm.

Ian