RH Designs ZoneMaste II and Pyro Developers
Has anyone tried to calibrate a ZoneMaster II using negatives developed in PMK or Pyrocat HD? I calibrated my ZMII using negs developed in "non staining" developers and see that the stain present on negs developed using PMK and Pyrocat confuse the ZMII. I expected this; I am just too lazy to try to figure out the adjustment on my own. I am certain one of my co-APUGers has already tried this and can provide insight & advice.
Thanks in advance.
I haven't experienced problems with stained negatives. Either tanol, finol, pyrocat, PMK or 510pyro.
As wild guess your problems may come from the change on your development more than by the stain itself.
Luis: are you suggesting that you calibrated the ZMII given the tools/methodolgy RH Designs provides and that your readings for stained negs are accurate?
Originally Posted by Muihlinn
Exactly. Also there it was a FAQ section about it in the old RH site.
I guess that's because it reads it as plain density, but cannot assure as I don't know about the internals of this meter, it works ok to me and that's all what I'm concerned about.
When I started out with it I did some calibrations that brought what seemed erratic results to me, so I repeated them with similar results. Then I learned two things: 1) judging those strips accurately isn't that easy as it seems when you're fine tuning 2) what was erratic was my early way of metering, I started to use the densitometer mode to check up the general contrast and my metering points helped to get used to the machine.
my 2c, hope it helps
Muchas gracias, Luis! I am going to double-check my readings.
Originally Posted by Muihlinn
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There might be some useful info or insights here:
in the section on the pyro model, and the instructions in the support area.
I went back and re-checked the ZoneMater II measurements with stained negs (PMK Pyro and Pyrocat HD) - no issues at all.
Meters need different calibration with pyro negatives because the paper sees stain as pure density, while the meter (any meter) sees stain as not much of anything at all. Interestingly, the spectral absorption of pyro stain resembles nothing so much as an OC filter. Some developer/film/process combinations produce a yellow-green stain - if this is seen as 'color' by VC paper, and thus effects paper contrast, I would recommend staying well away from any attempt at using a meter: it will waste your time and annoy the meter.
The real problem with metering pyro is that the stain density isn't always proportional to silver density.
However, in some serendipitous combinations the silver density and stain density follow each other quite well. Under these conditions calibration is easy, and any meter will work.
For the rest of the combinations, though, the ratio of stain to silver changes with negative density. It is possible to calibrate this out by having the meter's internal calibration change with changing negative density, and this is what the DA meter does. The instruction manual on the DA web site http://www.darkroomautomation.com/su...pyromanual.pdf (starting on page 7) gives detailed instructions on determining the needed adjustments. If it turns out that stain=silver in your process then you will have no trouble with any meter.
It is very important when attempting to meter pyro to maintain the same developing procedure for all your negatives. The silver-stain relationship seems to be influenced by changes in agitation. This is probably due to the way pyro quickly oxidizes and thus the activity of the staining developing agent declines in proportion to the activity of the second non-staining agent over the course of development. As development proceeds the density in the highlights (dense negative) builds more quickly in proportion to the density in the shadows (clear negative). As a result the ratio of stain to silver is different in the highlights and shadows.
Developers that oxidize more slowly will give more consistent results - PMK and PyroCat are two good choices.
You can run into cases where calibration works one time and doesn't another because the way the stain to silver ratio changes with agitation or developer age (with ABC minutes count).
You can also run into cases where one side of a bit of sheet film works fine, or the outside spiral of tank developed film works, but the rest of the sheet or roll doesn't meter properly. The reason is that the agitation of a sheet of film in a Jobo tank isn't consistent over the sheet, nor is it between the inside and outside turns of a reel. Try it - fog a sheet to ZV, develop it in pyro, bleach all the silver out and see if the stain is consistent across the sheet.
In my first investigations with metering pyro I just happened upon one of those happy combinations where the proportion of stain to silver is copacetic - and said to myself "This will be easy." Then I tried different combinations, just to make sure, and suddenly things went quite haywire. It took quite a bit of investigation to find out just what was going on.
I would approach metering pyro as an interesting exercise through which you will learn a lot about pyro and your technique. I wouldn't recommend metering as a way to increase darkroom productivity. If you want to increase productivity and decrease waste stick to D-76 1-shot diluted 1:1; then a good meter (there are only two: DA & RH) will work wonders.
Originally Posted by Nicholas Lindan
I'm sure that the reason I've been so happy with PMK negatives is my habit of developing in an inversion tank with very minimal air space in it (enough so that inversion actually moves the developer around). I never had any streaking even with less agitation than most people recommend, and the stain was moderate. But even so, at the end of a roll, the used developer retained zero activity, as evidenced by putting another exposed roll into it immediately as an experiment. Maybe the exhaustion of the developer was not entirely due to oxidation of the sort that would produce stain?
Well, developers work by getting getting oxidized. Oxidizing in the chemical sense isn't necessarily combining with oxygen but has to do with an atom's electrons.
Developer is a reducing agent (as an anti-oxidant, it has to be good for you) and 'donates' (in the chemical sense) an electron to the silver grain allowing a silver atom to break free, and thus the developer becomes oxidized. They same thing would happen if the developing agent combined with oxygen. Oxygen has an empty state in it's outer electron orbit - in it's natural state it hooks up with another oxygen and the two share their electrons. When oxygen is able to it will break up and stick to another atom that has an 'extra' electron in one of it's electron orbits.
Lots of simplification there.
See, as usual, http://en.wikipedia.org/wiki/Oxidizing_agent & http://en.wikipedia.org/wiki/Photographic_developer