Re: densitometer and pyro

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From: Clay (wcharmon@wt.net)
Date: 08/19/03-05:53:49 AM Z


Arie:

Phillipe's guidelines sound about right. But if you want some more
accurate information for your particular situation, the simplest and
most foolproof test, IMO, is to contact print the film you are using
with a Stouffer's step wedge using the BTZS procedure. Briefly, that is
a known quantity of light for 0.4 seconds (under the reciprocity wire).
This exposure can be done for you by anyone with an enlarger with a
light integrator/timer affair. Or you can have it done for you by The
View Camera Store in Phoenix. Anyway, take this exposed film test and
develop it normally in your staining developer. Measure the all-channel
white light densities of each step with your transmission densitometer.
Now contact print this new, stained wedge with the whatever process you
are using for a 'standard' time that will leave at least 3 or 4 of the
steps completely black, and a few completely white. Measure the
reflection densities of your print test. If you now plot the reflective
densities of the print (Y-axis) versus the transmission densities of
your stained test wedge(X-axis),you will have your very own film/paper
curve that will tell you exactly what the target density range of your
negative should be, without having to resort to UV densitometers or
anything like that.

I like this approach because everything is tuned to your own variables,
from negative development to the light used for your printing, and
makes no assumptions about light source wavelength, print process UV
sensitivity or anything else.

As Phillipe pointed out, each film is likely to have a different amount
of staining for a given silver density, so you would want to be careful
about extrapolating your results to other films without an independent
test. This is much less hassle than you would think.

Clay

On Tuesday, August 19, 2003, at 05:47 AM, Monnoyer Philippe wrote:

> Hello Arie,
>
> I don't have my charts at hand, but I can tell you that a density of
> around 2.4 measured in blue (do you have a color head with your
> densitometer ?) on a pyro neg (FP4+) is as dense as a 3.2 non pyro
> step. In other words, a 2.4 (blue density) pyro neg will print as a
> 3.2 (normal white light) unstained neg (for FP4+). The stain is very
> dependant on the film you use. For example, AGFA films hardly stain,
> ilford FP4+ and PANF are staining strongly.
> I have more detailed info. Yo can contact me offlist later.
>
> Philippe
>
> -----Original Message-----
> From: Arie [mailto:ariek@pacbell.net]
> Sent: Tuesday, August 19, 2003 05:07
> To: alt-photo-process-l@skyway.usask.ca
> Subject: densitometer and pyro
>
>
> Hi
> I was wondering if someone could give me some hints. I have a B&W
> densitometer but I process my negs in PMK. Is there a way I could
> trick the
> densitometer into giving me at least a ball park reading? such as a
> filter.
> If so which one, or can I use a rosco lighting gel? The other option
> that I
> figure is, has anyone calculated a factor that I can multiply my
> readings
> by? By the way the densitometer is a Tobias TBX
> Thanks
> Arie
>
>


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