PMK VS Pyrocat-HD Stuff

[sanking]

Originally Posted by sanking

I appear to have discarded the contact prints that were done with this set of negatives with the #5 filter.

Sandy

Kirk,

Although I discarded the contact prints made with the .52 CI negatives on VC paper with the #5+ filter I found the densitometer readings that I made of the prints before they were discarded. Curiously, although there is still a bit more compression in the highlights with the Pyrocat-HD print than with the PMK print the overall look is much closer on this print than with the .70 CI negatives printed on VC paper with a #2 filter.

I am fairly certain that this is due to the fact that the stain constitutes a much larger percentage of total density on the .70 negatives and therefore has a bigger impact on the way these negatives interact with VC papers. Then again, perhaps it is simply that the strong magenta color of the #5+ filter overwhelms the color of the stain?

In any event, the curve for the .52 negatives printed with the #5+ filter is attached.

Sandy

[Kirk Keyes]

Sandy - it would be interesting to see that graph with an adjustment to the exposure data (i.e. add or subtract a constant value to one or the other) so that the curves have a common middle point and then see how much difference there is on the ends of the curves.

But I suspect that you're seeing mostly the effect of the limited expsoure range of the grade 5 paper (VC or otherwise) - that's why they look so similar.

[Kirk Keyes]

It would be interesting to see Graph #2 with a correction for speed so that both curves share a common point, at say 1.0 print density. It would better emphasis the differences between them.

[sanking]

Originally Posted by Kirk Keyes

Sandy - it would be interesting to see that graph with an adjustment to the exposure data (i.e. add or subtract a constant value to one or the other) so that the curves have a common middle point and then see how much difference there is on the ends of the curves.

But I suspect that you're seeing mostly the effect of the limited expsoure range of the grade 5 paper (VC or otherwise) - that's why they look so similar.

Kirk,

I have not had a chance to think this through, but it seems to me that adding or subtracting a constant value to one of the curves would distort the curve in both the shadow and highlights, but primarily in the highlights, because of the different way the VC paper responds to the color of the stain.

You could probably get a more accurate idea about how the curves look reference to one another simply by shifting one up or down on the y-axis.

Sandy

[Kirk Keyes]

Originally Posted by sanking

Kirk,

I have not had a chance to think this through, but it seems to me that adding or subtracting a constant value to one of the curves would distort the curve in both the shadow and highlights, but primarily in the highlights, because of the different way the VC paper responds to the color of the stain.

You could probably get a more accurate idea about how the curves look reference to one another simply by shifting one up or down on the y-axis.

Sandy

It's not the y-axis I'm talking about - I'm suggesting that you add/subtract a fixed amount to one of the curves on the x-axis to slide one of the curves left or right so that the two curves overlap at one point, say at 1.0 on the y-axis. This will make a "correction" to your data so that both sets of data are "speed matched".

THis is kind of the same thing as printing both graphs out on separate papers with matching scales and then overlapping the papers, holding them up to a light, and then sliding the papers back and forth until the two graphs overlap at some point.

To find the amount of the correction, simply determine the difference between the two curves at your desired point. I've printed out Graph 3, and at 1.0 on the y-axis, the two curves differ by about 0.21 on the x-axis - so add 0.21 to the x-axis data from the Pyrocat curve, or subract 0.21 to the x-axis data from the PMK curve. This will make the print densities on the two curves overlap at 1.0.

This doesn't shift highlights or shadows differently because you apply the same "correction factor" to all the exposure data points on that one of the curves. It may not be something you can do in the WinPlotter software - something like Excel would do this very easily.

Doing this will make the difference between the two curves more obvious.

[gainer]

Yes, you can add a log relative exposure amount or a density amount without changing the shape of a curve. I think Sandy has done his job. All we need is to make 2 copies of the graph and lay one atop the other on a light box or a bright window to compare curve shapes.

[jim appleyard]

I've seen an advantage. I've found that my midtones are quite long in scale and it does show up on VC paper, even on generic Adorama VC. However, that's just an unscientific observation; only my opinion.

[Donald Miller]

I have seen an advantage with staining developers with VC materials. As previously stated, there is much better midtone and highlight tonal separation. The only staining developers that do not exhibit this characteristic are those with a green or yellow green stain. Developers that this would include would be ABC or PMK formulations.

[Donald Miller]

Originally Posted by jdef

Donald,
Sandy's curves don't show the differences in midtones that you describe between PMK and Pcat, and suggest PMK might offer better highlight separation, depending on the subject. How have you measured these differences between pyro and catechol based developers, or between staining and non-staining developers?

Jay

I have exposed and developed negatives that were contact printed with a Stouffer step wedge. The films were Efke PL 100 and Tri X. I then printed these on Oriental Seagull VCFB and JandC Classic Polywarmtone and then read the resulting print densities with my Xrite 310 reflective densitometer. Hope that this helps.

[Donald Miller]

Jay, It has been some months since I did the testing. I will check to see if I still have the values somewhere. I will post them here if I locate them.