I like that Ralph!
PE
PE
The effect of pyro stain on VC paper contrast.
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Gawd - I get accused of that one all the time here...
But there are some things, like the action of pyro stains with VC paper, that are certainly more complex than many people seem to think.
Join the club!
PE
PE
I have to disagree with this statement - the spectral scans I made clearly show the stain is anything but "simple density".
Are you saying the links I put in my post are not working? They do for me. Let me know if that's the case and I'll see what I can do.
I think it's more like having a #2 filter in the shadows, a #1.75 filter in the middle densities, and a #1.5 filter in the highlights.
So the pyro stain lowers the contrast in the highlight relative to the shadows, but only by about 1/2 paper grade. And there are certainly times where that is a useful feature to have in a developer. You can't get that out of Rodinal or XTOL or any other non-staining developer.
Ralph, I agree with what you say here, and with the variables that HRST mentioned above. It can be a very complicated. And I was looking into some of those variables you both mentioned. I bought a Minolta Colorimeter so I could measure the color temp of the light sources I was working with.
I was also working on making a recording spectrometer so that I could measure the amount of density recorded on various papers at from UV through the visible wavelengths using different filter packs or pyro-developed films to compare the differences.
It would make spectrograms like PE showed a few posts earlier in this thread. I've got a beautiful 4 inch diameter spherical mirror with a diffraction grating etched across the face of the mirror for this project. The mirror is in a brass mount and it must weigh 10 lbs or more. But then I had a wonderful little girl nearly 5 years ago and I found I had a lot less time for projects like this.
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If that's the case, it could explain why pyro negatives work better with fixed-grade papers, because it would not work well with a long and constant toe paper such as MGIV. Printing in the highlights demands a higher grade to get more separation into the highlights. I usually start soft for the shadows and add contrast into the highlights. I would be interested in the opposite effect of what you describe!
But again, how does what you describe affect fixed-grade papers and why, since they do not respond to filter changes?
I took the #2 for the highlights in my statement as that was the assumption from the data Nicholas posted, but there's such a wide variance in stain colour and intensity that figure could easily be #1.5 or even as high as #3
Ian
Apparently they do respond slightly to filter changes, there's a couple of threads on APUG on the subject.
Ian
Thinking about it again, that makes sense as far as print density is concerned, since they have a non-uniform sensitivity across wavelengths, and it could affect contrast if the emulsion is made of differently sensitized salts.
I agree. The optical density consists of the diffuse density and the specular density ( Applied photographic optics: lenses and optical systems for photography, S. F. Ray, p.16). Without stain there is a mix of the two densities. With stain the diffuse density will increase. These densities are a function of many parameters, grain size, grain structure, spectral distribution of the incident light etc. etc. Really complex.
Jed
Better with non-VC papers? It all depends on what you are looking for, I think. I use pyro developers for scenes that have high contrast to compress the highlights.
Ralph;
It is actuaally behaving as a variable neutral density and so will affect all papers. The difference in contrast = the difference in speed between no filter and the presence of the filter as a function of density in the scale. Thus, go back to the curves posted by Nicholas and see that if you draw a curve that fits between those two curves, this is the actual paper contrast.
PE
Yes, as PE says - with non-VC papers, the stain acts as if it is regular, old silver in the negative, as far as optical density goes. It does make it a little hard to use your densitometer to figure out contrast index of stained negs, as the density in the print is still dependant on the spectral properties of the paper and how it reacts to the stain. When using a color densitometer to measure a pyro neg, you will get a higher CI on the blue channel, somewhat lower CI on the green channel, and lower again on the red channel. The visible channel on the densitometer will be somewhere in the middle of all that. And a UV densitometer gives a higher CI than the blue.
Of course, all that should be expected after looking at the spectral scans of the stained negs that I posted earlier.
Which one is right? Well, none is "right"... it all depends on how the paper reacts to the stain.
Of course, all that should be expected after looking at the spectral scans of the stained negs that I posted earlier.
Which one is right? Well, none is "right"... it all depends on how the paper reacts to the stain.
Well, Kirk, technically you need a UV densitometer if your light source has an appreciable amount of UV in it! 
This can offset or negate anything you read otherwise. And, this will be magnified in a contact type paper vs an enlarging paper.
PE
This can offset or negate anything you read otherwise. And, this will be magnified in a contact type paper vs an enlarging paper.
PE
That would be cool to have a developer that builds contrast in the highlights.
This brings up the color of the stain. I'm no expert on staining negs, but I always see reference to people calling negs from PMK as yellowish-green. My PMK negs never really show much color other than a yellow tint. So I solicited negs from APUG and Photo.net members years ago, and I actually had 5 people respond and send some negs developed in PMK for me to play with. All of the negs I was sent were what I would call yellowish in color, and I personally did not see much green in them.
Pyro developers are often recommended as "compensating" developers when used with VC papers where one wants to compress the highlights. It's because of this yellowish stain in the highlights that acts as if you are adding yellow filtration proportionally to the silver which softens the highlights with the VC paper.
Ideally, to do this, the stain would make a very pure yellow color in the neg to filter out blue light strongly. Unfortunately, it does not do this and as we can see from Nicholas' scan of the VC filters and the PMK neg, the PMK neg is not very saturated or pure in color.
To make the opposite effect as you desire (highlights expanded and/or shadows compressed), we would need to find a developer that makes a proportional magenta stain in the highlights. I suppose if we could find a developer that had a bit larger ring structure or some more conjugation than pyrogallol or pyrocatechol, maybe that could extend the absorption out to the green from the blue.
Note that Xtol makes a very slight magenta stain that can be seen if you bleach out all the silver from the neg. It's not very strong, about 0.03 density, so it's really not useful for this purpose.
I'm sure PE could devise a way to make a film that could be used either for highlight compression or highlight expansion by using either a yellow dye or magenta dye and coupling it with silver as the film develops. That way either color of dye would be added to the film during development to achieve the affect that the photographer desired.
Well, Kirk, technically you need a UV densitometer if your light source has an appreciable amount of UV in it!
This can offset or negate anything you read otherwise. And, this will be magnified in a contact type paper vs an enlarging paper.
I don't have a UV densitometer proper, other than a spectrophotometer. I'm reporting info there from what I've discussed with people that do have UV densitometers.
But it does show how complicated measuring these things can be.
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And the step wedge exposed through the heavily stained negative shows how many steps??
And the step wedge exposed to the unstained negative shows how many steps??
Why can't we just post our step wedge tests and be done with it.
And the step wedge exposed to the unstained negative shows how many steps??
Why can't we just post our step wedge tests and be done with it.
Because we don't know which two to compare. What gradient to you want them developed to, and how do you want to do that with two different developers?
Just a thought for a simple test. Expose a step wedge on two pieces of film. Develop one in non-staining developer and use a staining one for the other. Bleach the silver off the stained negative. Contact the neg with the non-staining on VC paper. Then do it again, but this time lay the stained neg over the non-stained neg. Compare the contrast.
Vaughn
Vaughn
Well, we do not know the form of the silver that is created by the staining developer, do we? Silver itself has color! It can be warm or cold toned. We cannot see it through the "stain". That further complicates the test.
PE
PE
I suppose, but I'll leave that to those who prefer the picking of nits over the making of prints. I am waiting for my sensitized carbon tissue to dry so I can make prints...but I may go out for some Chinese first.
I am waiting for my sensitized carbon tissue to dry so I can make prints...but I may go out for some Chinese first.
Moo Shi Pork, or Pekin ya. Mmmmmmmmmm. Egg rolls, spring rolls, Lo Mien. Gung Pao Chi Ding! Yum. Have fun.
PE
PE
Back from dinner. We here in Humboldt County are still paying off the bad Karma of the late 1800's when the county shipped all the Chinese down to San Fransisco. No great Chinese food to be found. The karmic burden we have for what we did to the Native Americans is another matter...
Vaughn
Vaughn
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