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View Full Version : Pyro stain v catechol stain re: VC paper



Jay DeFehr
7-Jan-2007, 00:24
Hi all.

Before the thread on PMK v Pyrocat, which includes a lot of information about printing stained negatives with VC papers was closed, we were discussing the effect of the different colors of the stains produced by pyro and catechol developers on VC papers. Jorge and Sandy were adamant that the two types of developers produced negatives that print diffrently with VC papers because pyro stain is green and catechol stain is brown, and Jorge specifically called for some supporting data to show why that's not true. I described my simple test for this in the other thread, but I'll repeat it here for those who might be intersted, and don't want to dig through that thread to find it. My premise is that pyro and catechol negatives that are matched in density as measured by Blue channel densitometry will require the same amount of Magenta filtration to neutralize, and will produce the same print density with VC paper. To test the premise, I made negatives in pyro and catechol developers that match in density as measured by Blue channel densitometry. Using my color analyzer, I determined how much Magenta filtration was required to neutralize the light on the easel with each negative in the carrier, then I printed the negatives with the indicated amount of magenta on VC paper. When the paper was dry, I measured the reflection densities of the prints of the respective negatives. Here's the data:


Film: Forte 100

pyro developer: 510-Pyro

Catechol developer: Hypercat

Paper: Arista Edu Ultra RC VC Semi-matte.

Print exposure: 5.6 sec./ f 5.6

filtration: 40M

Negative densities as measured by Blue channel densitometry:

Pyro- 1.22

catechol- 1.21

Magenta filtration required to neutralize the YFE:

Pyro- 42M

Catechol- 40M

Reflection print densities:

Pyro- .43

Catechol- .44


As the data above shows, when the negative densities match as measured by blue channel densitometry, they will require the same amount of magenta filtration to neutralize, and produce the same print density with VC paper. Any differences in the colors of the stains produced by pyro and catechol developers are insignificant relative to printing with VC papers.

Jay

Ralph Barker
7-Jan-2007, 07:42
This information will be allowed to stand, but no need to rehash the same issues.