[pure-silver] Re: Any advice for purchase of densitometer.
- From: john stockdale <j.sto@xxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Thu, 23 Dec 2004 08:24:55 +1000
At 10:04 PM 22/12/2004, you wrote:
>.....The Heiland products are specifically black and white so should not be
>affected by the stain colour. However the article that Tony refers to
><http://www.unblinkingeye.com/Articles/Densi/densi.html> is interesting,
>and suggests that a b+w densitometer will not take account of the stain. I
>will ask Juergen Heiland about this and report back.
>Regards
>Richard
Thanks Richard, that would be interesting. The article to which Tony=20
referred seems to agree with Sandy King's observation that a UV channel is=
=20
a good predictor of effective density for alternative processes, but that=20
for silver printing, especially VC printing, the effect of different hues=20
of dye are difficult to measure using, for example, blue and green channels.
Since the stain of pyrocatechol film developers is moderate and brown (at=20
least in the visible spectrum) rather than the olive green (and sometimes=20
quite strong) of PMK, I was prepared to just measure the silver density=20
and be aware that there would be some additional contrast. The fact that=20
there is density in the UV would probably not affect me, I'm guessing. I'm=
=20
sure that graded and VC silver papers are senstitive to UV, but how much UV=
=20
is produced by a 2-tube VC head, and would it pass through an enlarger lens=
=20
anyway? In his web site about Nikon lenses, Bj=F8rn R=F8rslett mentions=
one=20
enlarger lens that passes UV, so are we to conclude that most don't?
So if I know that a densitometer was in fact giving me just silver density,=
=20
I would be happy enough. I could then compare the effect on paper of=20
stained and non-stained negatives of approx equal silver density, and make=
=20
up a table of adjustments.
John
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