PMK VS Pyrocat-HD Stuff

[Kirk Keyes]

Excellent question, Sandy. Of hand, I would suggest that Jon repeat that test.

But upon thinking about it, I can tell you that I did some spectrometric analysis of Ilford Multigrade filters last year and I can tell you the magenta filtration that is in the filter shift depending on the filter grade. On the filters grade 3.5 and below, they have the same central wavelength peak, while the filters grade 4 and above, use a different peak wavelength. I assume Ilford does this to help speed match the two sets of filters.

Perhaps it is this difference that is making the prints act differently. If Jon is using a dichroic head, than all bets are off and I again suggest that he redo the test to verify his claim.

Kirk - www.keyesphoto.com

 

[gainer]

One thing we must consider when it comes to filtering stained negatives is that the filter's color is uniform, while the negatives color saturation (if that is the right term) varies with the image silver. If we had a blue filter in a dichroic head, as some do, We might see that as the filter strength is increased, the stain image image below some level is more blue and above it is more green. This is not a simple thing to analyze, because the paper local contrast should be higher for the part of the image for the image that lies below the blue level of the filter and lowr for the part above. Am I making myself perfectly unclear?

The magenta filter is minus green and the yellow is minus blue, of course. That doesn't make it any easier for me, but maybe it does for you guys.

Jay, all you have to do to check me out is the experiment I described. Bleach out the silver leaving the stain image. Print the thing on graded paper. I did that once for the public when I wrote the article "More Pyrotechnics" a few years ago.

 

[Jon Shiu]

Nevermind...

Am I reading this right? Your WD2D+ negative printed with more contrast with a #3.5 VC filter than with a #4, #4.5 and #5? And did you verify the results with a second printing?

Assuming John's experience can be repeated, anyone have an idea why this might happen?


Sandy

Hi, I just did a re-test and the filters worked as they should have. I suspect that the developer at school was weak.

Jon

 

[sanking]

Hi, I just did a re-test and the filters worked as they should have. I suspect that the developer at school was weak.

Jon

Thanks for the report.

Well, it was interesting to speculate, right?

Sandy

 

[Bulent Ozgoren]

I use FP4+ 4x5", develop in Pyrocat-HD 1:1:100, print on Forte Polywarmtone VC with VCL4500 using split grade printing. My usual figures are (X-Rite 310 Blue Channel) Zone I,5=.17 and Zone VIII,5=1.38. In order to develop to CI 0.70 what Zone VIII,5 density should I aim for?

 

[sanking]

I use FP4+ 4x5", develop in Pyrocat-HD 1:1:100, print on Forte Polywarmtone VC with VCL4500 using split grade printing. My usual figures are (X-Rite 310 Blue Channel) Zone I,5=.17 and Zone VIII,5=1.38. In order to develop to CI 0.70 what Zone VIII,5 density should I aim for?

At one time I thought that the major factors that determine effective printing contrast of a stained negative with VC papers were the color of the stain and the spectral sensitivity of the paper. However, I now think that the radiation of the exposing light as well as the brand of variable contrast filter being used also play major roles in determining printing contrast. This greatly complicates the issue of sensitometry with staining developers and VC papers.

Someone could most likely pull all of these variables together and provide useful guidelines. But it would require, I think, someone with a real interest in printing with VC papers.

Sandy

 

[sanking]

Sandy,

you raise an interesting question, which is; how important is sensitometry with VC papers, in practice? Why go to the trouble of making sensitometric measurements of negatives to be printed on VC paper, when it's much more practical to scale the paper to the negative? Isn't that the biggest advantage offered by VC papers?

Jay

Sensitometry is a system that should allow us to anticipate and achieve a desired density and contrast on the print, based on a reading with a densitometer of negative densities. For that reason it's use with silver VC papers seems no more and no less important to me than with processes like carbon, kallitype, pt/pd where we also have the ability to control contrast, not with filters as with VC papers, but with changes to our emulsion or sensitizing solutions. There is no question but that these controls, which offer the ability to adjust the process ES to suit the negative DR, offer a big advantage over printing with a process where contrast control is limited, as in graded silver papers or Vandyke. However, even with these controls it seems reasonable that one should aim for a negative that will print somewhere in the middle of the ES of the printing process. This provides some degree of latitude for interpretative or technical mistakes made during exposure and development.

Sandy

 

[sanking]

Is densitometry/sensitometry really necessary to produce negatives that will print within the middle grades of VC papers? It seems to me that the degree of precision required to produce negatives that will print on middle grades of VC papers can be acheived readily by simple trial and error adjustments.


Jay

By virtually any standard one might apply sensitometry is, practically speaking, not necessary. I would estimate that more than 98% of the prints produced during the history of history were made by persons with little or no knowledge of sensitometry. Anyone who is satisfied with simple trial and error adjustments should feel free to continue to work that way.

I appreciate sensitometry because it gives me a greater degree of precision in my work, saves a lot of time, and enriches my understanding of the materials of the medium. On the other hand I don't have a a lot of interest in printing with silver VC papers and don't have the time to do the kind of testing that would be necessary to determine exactly how much precision one can get with these papers when printing with stained negatives. It is very possible that with the right choice of filter in the measuring densitometer one could get almost as much precsion as with graded papers such as AZO and UV sensitive processes such as carbon and Pt./Pd. but I guess that is pretty much speculation at this pont.

Sandy



Sandy