PMK and Densitometers

[William D. Lester]

In an earlier post, (Re: Densitometer Numbers - What they Mean),Steve Simmons wrote 'I like a density of 1.35above fb+f with PMK and Gordon Hutchings likes a density of 1.6 or a little above with PMK. Of course, with a staining developer blocking high values is much less likely'

I assume that Steve is using a colour densitometer when reading PMK negative densities. Are all of the target densities then the same as film developed in conventional developers? What happens if you use a black and white densitometer?


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[fhovie]

My Densitometer reads both. There have been some fine articles written about UV response. I will only report what I have observed. I use a condenser enlarger with no UV filter. I use graded paper. When I set my development times, they are set for the standard channel. When I measure the UV channel, The densities are far greater. For a density of 1.5 in standard mode, I will often get 1.8- 2.1 or higher in UV mode. I know that my graded paper has a UV response and the incandescent bulb in my enlarger gives off a little UV. (Omega D6XL) I am sure that there is a small contribution to contrast from the UV and I am also sure my prints are better for it (I don't see the same contrast boost from VC papers and the stain has a negative effect of reducing local contrast - that I have observed directly)

From my observations and experience - the UV channel is interesting but not terribly useful when used with my enlarger and papers. Maybe an enlarger that has more UV or papers that have a greater response from UV would make this channel more useful. I believe the UV content in my negs (from observation using different papers and compared with negs developed in XTOL) is worth 1/2 grade harder in my prints compared to a non staining negative. I am not sure how different the results are with pyrogallol versus pyrocatechol - I would guess the outcomes are similar.

I used PMK for years and now use Pyrocat. They are very similar in outcome. The PMK had slightly larger grain in my opinion. It was not much of a factor for sheet film but enough of a difference to effect roll film - for my taste. There are some who will make the case that PMK has better highlight control - maybe so - but semi stand processes and different dilutions and times can tame any negative. So - I will continue to use p-cat till the cows come home for anything that doesn't need to get pushed. (I still keep pyrogallol on the shelf and sometimes make 510 Pyro or PMK for a specific task)

[steve simmons]

but semi stand processes and different dilutions and times can tame any negative

This is not the same thing at all. What a staining developer does is not push the silver densities up onto the shoulder giving better seperation. A compensating development process like stand can not do exactly the same thing.

When reading a stained neg most people use the blue channel. When I gave the densities for myself and Gordon I was giving numbers obtained through the blue channel. Gordon is giving a presentation on using and understanding staining developers and another presentation on understanding film curves at the View Camera conference.

You can do your testing with a densitometer or use the Picker testing method. His procedure works well with staining developers. If you use vc paper use either no filter or a #2 filter. If you use graded papers use grade 2. That gives you plenty of room down the road to adjsut your printing in any given situation up or down in contrast. The Picker method is described in an article in the Free Articles section of the View Camera web site,

www.viewcamera.com

We have an article on staining developers in an issue late last year in an attempt to answer these questions.

steve simmons