sstoney@pdq.net
Date: 10/14/02-08:26:45 AM Z
Sandy wrote:
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.
That's what I do. I find Zone II and then the highest zone that I want to
print, and the difference is the SBR.
>
>>
>>
>>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.
I tested times of 5.5 through 22 minutes. The only reason I can think of
that I get such a narrow range is that I am using tubes. It seems like
when I processed 4x5 negatives in one of those Combiplan tanks, there was
more difference between a 5 minute development and a twenty minute
development. But you can't use those tanks with 8x10 film! I like the
tubes, and now that I"ve calibrated everything to them I suppose I should
stick with them. But I'm thinking of switching to trays and development
by inspection, now that I have a well ventilated place to work.
>>
>>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.
Do you use the same film speed regardless of what process you are shooting
for? What if you were planning to make a palladium print? Would you
still use the same ISOs as you would for silver?
>> 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.
Yes, i mean for the film. What I mean is, I thought people probably used
different film speeds when shooting for different processes. That is,
sometimes people say to use a faster film speed when shooting for pt/pd
for example, because you plan to develop the film longer, for a given
density range. Therefore your shadows might get too dense unless you
underexpose the shadows a little.
For example, my tests show that for cyanotype, if you are looking at a
scene with an SBR of 6, you need to develop the film for 16 minutes; but
for Azo, the same scene needs a development time of about nine minutes.
Let's say you make two negatives of this scene, one for printing in
cyanotype and one for printing on Azo. Then you develop one for sixteen
minutes and one for nine minutes. The shadows on the nine minute one are
going to be a little less dense than the shadows on the sixteen minute
one. Therefore you probably should have shot the sixteen minute one at
say 400, shouldn't you? This is what I thought the tests were going to
tell me, and they didn't.
> .
>>
>>I'm beginning to think that developing by inspection is looking more
>> and more attractive...
>
>
> 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!!
Can't you tray develop more than one sheet at a time?
--shannon
> --
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