[pure-silver] Re: AW: Re: Any advice for purchase of densitometer.
- From: Sandy King <sanking@xxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Fri, 24 Dec 2004 17:31:48 -0500
I pretty much agree with what Juregen wrote about the problem with VC
paper. In fact, I would go so far as to say that for VC papers a
densitometer that reads only in Visual mode will be at least as
useful as a color densitometer that reads in Blue, perhaps even more
so. However, even a reading with a B&W densitometer will probably
indicate a density range that is actually less than the effective
printing density range of a stained negative with VC papers, and this
is due to the fact that VC papers are sensitive to both blue (high
contrast) and green (low contrast) light.
Sandy
>Sandy wrote:
>
>>There is of course no constant factor that one can add to the Blue
>>reading to approximate UV readings because the stain increases
>>proportionally to silver density.
>
>The word "Proportional" suggests an arithmetic relationship, but
>multiplication by a factor instead of (or as well as) an addition.
>
>My intention was to use an ordinary "black and white" densitometer and to
>adjust my readings by a simple formula that I would estimate from
>comparing non-stained standard density tablets from Stouffer with my
>stained negs after contact printing them together on the various papers
>that I use under my own VC head, which would have its own characteristics
>(including an unknown amount of UV).
>
>What I wanted to know originally was:
>With a "black and white" densitometer, what do you get with a silver+stain
>negative? Richard Ross has kindly provided me with some info from
>Juergen Heiland which suggests that i would not simply be getting the
>silver-only reading, but silver+(unknown part of the stain)
>
>
><start of quote>
>Juergen says "the B&W densitometer measures a large spectrum around the
>maximum sensitivity of the human eye (green colour) it will also measure
>yellow, green or brown stains. The problem of interpreting the density
>values (translsate them into filter setting) is caused by the point, that
>if you print the negative on a multigrade paper, you use the Yellow and/or
>Magenta filter. In case of a stained negative the resulting filter is
>different from the enlarger filter. I.e. both filter values are changed.
>Also the stain is more colourful in the highlights (darker parts of the
>neg.), compared to the shadows. This fact leads on one side to the
>wonderful highlight details, that are one of the main reasons for using
>pyro. On the other side it shifts the necessary light and shadow exposure
>into two different directions.
>In other words: The densitometer reading of pyro negatives is not so useful
>as the one on colour neutral negatives."
>So IOW the density reading from a pyro negative may not be an accurate
>guide to the required contrast filtration if you're using VC paper - which
>is fair enough. As the instrument measures a wide colour spectrum it will
>presumably read both the silver and stain densities and give you an
>effective total.
><end of quote>
>
>I am not so concerned about choosing VC filtration from a densitometer
>reading. I just wanted to make some tests and then make some decisions
>about materials (speed, dev time etc), after which I would go on my merry
>way without taking any more measurements.
>
>I could do this without a densitometer, but I want to do a number of tests
>and having measurements seemed like a way to save some time(!)
>
>I am planning to acquire a black and white densitometer and i'll make some
>comparisons and offer my results for what they're worth.
>
>Thanks to everyone for their insights and experiences.
>
>
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