From: Scott Wainer (smwbmp@starpower.net)
Date: 04/08/03-04:29:55 PM Z
Hi Jack,
For my tests I:
1. Taped a piece of white mat board to a wall outside in open shade
2. Set up my camera so that the board filled the viewfinder
3. Set the focus at infinity
4. Metered for zone V using the manufacturer's rating of 125
5. Calculated exposures for zones 0 to X
6. Made 3 sets of exposures for zones 0 to X on each roll; plus
additional exposures for zones I and VIII (keeping all exposures
between 1/500 and 4 seconds; including reciprocity)
7. Develop according to manufacturer's recommendations for each
developer
8. Read and average densities for each zone with a B&W densitometer
9. Plot densities on graph paper and find where the curve crossed the
0.10 density line to find the film speed
I shot 3 rolls of film for each of the 3 developers (FX-37, D-76/ID-11, and
Xtol) I tested and came up with very similar results for each. The first
roll with each developer was processed using published recommended times.
For the second roll with each developer I tried minimal agitation by
increasing the time by 100% and agitating every third minute. The third roll
was developed using increased dilution and adding 100% to the times. Each of
the nine tests showed almost no density (about 0.01-0.03) above fb+f below
the zone III exposure. My tests with Pyrocat-HD also showed the same results
though the stain makes those tests useless. Each developer was mixed from
raw chemicals about an hour before development.
Published times for Arista Pro 125 (aka Ilford FP4+) state that:
EI should be 160 in FX-37 (1+3) for 4.50 min at 68F
EI should be 200 in D-76 (1+1) for 11.00 min at 68F
EI should be 250 in Xtol (1+2) for 13.75 min at 68F
My tests show that the EI in these developers (at the above dilutions and
times) is 12-25. Much, much lower than published data. I thought that the
chemistry might have been bad, but tests done with 400 speed film in the
same chemistry show EI's of 250-320. I am at a loss as to what is going on
here. I should be getting film speeds close to manufacturer's specs if not
better.
Scott
smwbmp@starpower.net
----- Original Message -----
From: "Jack Fulton" <jefulton1@attbi.com>
To: <alt-photo-process-l@skyway.usask.ca>
Sent: Monday, April 07, 2003 11:40 PM
Subject: Re: Film Speed and Negative Development
> Just off the top of my head, and based upon experience with Ado ISO 12
film
> of many years ago . . though you rated the film @ whatever ISO was
> indicated, did you BRACKET? That's the key to find the correct speed.
Then,
> once speed is derived you can judge development time by observing the
> contrast.
> Jack
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