Re: Fortespeed 412 (and a Question)

Hi Tom,

----- Original Message -----
From: "Tom Miller" <tomwmiller@comcast.net>
To: <pinhole-discussion@spitbite.org>
Sent: Wednesday, November 17, 2004 8:09 PM
Subject: RE: [pinhole-discussion] Fortespeed 412 (and a Question)

> This does make sense to me. Here is a link to a topic on Tom
> Persinger's f295 forum. It shows a test I did last summer with and
> without using a yellow filter to improve the tonal range.
> http://f295.tompersinger.com/cgi-bin/Blah/Blah.pl?b=lab,m=1100713642

Wow, this is a very definite proof that I'm on the right path! Thanks for
providing this; it was very helpful. I see that you used a (#8... or is it
#12) yellow filter designed for B&W film - because yellow jel filters make
the image fuzzy. I won't be using filters designed for panchromatic films.
Will simply use a 00 grade Multigrade filter for my experiment. The tech
sheet says the paper's speed drops by 1 stop using that filter (P500 to
P250). I remember someone (Guillermo?) stating it's good to assume ISO speed
of paper to be 1/100th of paper speed - so I plan to rate the paper ISO 2.5
for my experiment (taking into account the effect of the yellow filter). If
that works I'll be saving 2 stops! (I'm not willing to tolerate exposure
times more than 20 - 30 minutes)

> ... The more layers of filter, the fuzzier the image became.

Well, I'm ready to tolerate some fuzziness in exchange of speed. As I will
be using a laser drilled pinhole (at optimum focal length) I'm already
starting with the best quality possible...

> The question (to Loris or anyone on the list): I look at the spectral
> sensitivity charts that come with paper or are in the manufacturer's
> technical specification sheets on their websites. They make sense to
> a point; I can read from them that an emulsion is more or less
> sensitive to a particular wavelength of light. Could you give me (and
> us) a little more information about what these charts are telling us;
> or is there a link on the internet that would give a non-scientist a
> good explanation?

I didn't evaluate the sensivity charts and contast curves in a too
scientific manner. I plan to use the negatives to make pop palladium prints
(specifically: Ziatypes. And yes, I know that RC base is UV opaque... will
scan the negatives and re-make them digitally on UV transparent media). As
platinum/palladium prints are best known with their long, delicate and
smooth tonal rendition, I wanted to start with the best negative possible
(in other words with a negative that registered as much tones as possible);
POP Platinum process is able to print even the slightest tone in the
negative (thanks to the self-masking phenomenon). So, I looked for a paper
that has the widest sensivity range (variable contrast papers in this case -
single grade papers are only sensitive to blue, ITOH variable constast
papers are also sensitive to green) + I inspected the curves to find the
mildest one which is the most linear at the same time (in this case the
curve that results when a 00 grade filter is used).

Please correct me if I'm wrong in any of my assumptions (including friends
from the alt. process list).

Regards,
Loris.

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Received on Wed Nov 17 14:13:44 2004