From: Sandy King (email@example.com)
Date: 10/13/02-05:30:20 PM Z
>The high of 10 or 11 is true for cyanotype, but for azo the highest SBR
>covered by this test was about 7.4. Also, the way I determine subject
>brightness range is with a reflection meter rather than an incident meter.
> Does this make any difference?
The issue with the limited range of SBRs is probably due to the fact
that your shortest and longest development times were too short and
not long enough. As for the method of determining SBR I assume one
can do that accurately with a reflective reading if they know what
they are doing. In my own work I either use incident readings to
determine SBR or work with a spot reflection meter when I want to
work with Zones.
>Actually it goes from N to N+ 1.66.
That seems very strange. My tests with TRI-X and Pyrocat, when the
specified DR is 1.4, give a range of N-3 at 4 minutes of development
to N+1.5 at 14 minutes development.
>Yes. The trouble is, only the Ilford curves show the ISOs for the
>different curves. On the Azo chart, the ISO squares were left blank. Am
>I to assume that the ISOs for Azo are about the same as for Ilford?
>This is my main question.
The ISO, which in this case is really an effective film speed, is
related to time of development. It does not matter whether you are
developing for Ilford or Azo in this instance.
>OK. I used to figure this out just by printing a step tablet and then
>experimenting with film development times until I got a time that yielded
>the right density for that paper. The problem was, this test had to be
>repeated for every subject brightness range. I thought if I did this test,
>I would know all the SBRs and their corresponding development times and
>ISOs at once.
Yes, you should get enough information from the tests to indicate
what time of development you would need for a range of SBRs, and the
effective film speeds as well, but only for the two DR ranges (= same
as Ilford 1.24 and AZO 1.38). If you need another DR you will have to
run the Plotter program again.
> He said I could use the same ISOs for
>all four papers, but could this really be true?
I assume you are talking here about effective film speed for the
film? The ISO of your papers is basically irrelevant since you can
control this with time of exposure.
>IF this were true it would be convenient because you wouldn't have to
>decide how you were going to print a negative until later, when you went
>This is in fact true and it is one of the wonderful things about the
>Davis method of testing.
>I'm beginning to think that developing by inspection is looking more and
One sheet at a time? Thanks, but not for me. Well, maybe for a really
big negative when I have a lot of questions about how it was exposed!!
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