From: Tom Ferguson (tomf2468@pipeline.com)
Date: 10/31/02-10:23:17 AM Z
In my experience what you are seeing is the unpredicatble (batch to
batch) variation in extreme reciprocity numbers. One "batch" of film "X"
will be nearly identical to another batch at 1, 2, 4 seconds. Beyond
that you get move variation.
Simmons errors on the side of too much exposure. Make sense for silver
gelatin work. But we are usually over developing our film and then
giving annoyingly long UV exposures. A "too much" exposure neg can be
real dense and slow to print :-(
For my own work with T-Max 400 and HP5 for alt I find Simmon's a little
too much and the manufacturer's a little too little. I split the
difference. Also remember that that extra 90 seconds sounds huge (your
200 versus 290seconds example). But, it is really only a 1/2 stop
difference.
On Thursday, October 31, 2002, at 07:21 AM, Shannon Stoney wrote:
>> Shannon wrote:
>>
>>> Sandy wrote:
>>>
>>>> There is a reciprocity correction chart for Kodak, Agfa, Ilford and
>>>> Polaroid B&W films on p. 75 of Simmon's Using the View Camera.
>>>> Nothing on Fuji.
>>>
>>>
>>> This chart gives even longer times than the Kodak online chart does.
>>> So I assume if I had used it, my negatives would have been even more
>>> overexposed! At least, at the higher end of the scale. At the lower
>>> end, they're about the same.
>>>
>>> --shannon
>>
>>
>>
>> Overexposure takes place in the camera. If your negatives have a very
>> high density reading at the lower end of the scale you gave too much
>> exposure when exposing. CI or DR is controlled by time of development.
>> We normally develop to get the appropriate density range for our
>> process, and the low values just have to fall where they will.
>
>
> Whoops, I wasn't clear here. What I meant was, the two charts
> (Simmons' and Kodak's) give about the same adjusted times when they are
> talking about 2 second or four second meter readings. When you get up
> to say thirty seconds, the Simmons chart gives 290 seconds for the
> correct exposure, whereas the Kodak chart says 200. That's a big
> difference.
>
> --shannon
>
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