From: Tom Ferguson (tomf2468@pipeline.com)
Date: 04/08/03-06:33:10 PM Z
Scott, something is odd! In "general" using the 0.1 over FB+F (fine for
silver gelatin, not so good for many/most alt processes) you will get
"about 1/2" the company rated value (FP4 rated at 125, personal EI 64 or
80). Different developers don't change it that much :-(
For you to be getting "3 to 4" stops lower (EI 16 to 8) indicated bad
developer,bad testing technique, bad meter, or bad film.
For alternative process work a good "general" rule is to decrease your
"silver/0.1/Adams" EI test by 2/3 stops. If your FP4 manufacturer is ISO
125, "silver/0.1/Adams" test is EI 64, use EI 40 for alt. That is very
"general". I have an article you can read about film testing for alt
processes at:
http://www.pipeline.com/~tomf2468/altinstruct09.html
But again, for you to be getting " 3 to 4 stops" (as opposed to my
"estimated" 1-2/3 stops) is odd enough that I "assume" something is
"broken or bad".
On Tuesday, April 8, 2003, at 04:36 PM, Scott Wainer wrote:
> Greg,
>
> I can almost live with whatever film speed I get. I thought that it
> might be
> about 1/2 - 1 stop less, I just didn't expect it to be 3-4 stops less
> than
> what the manufacturer rated it at. If that is truly the case then I will
> just go back to shooting Pan F+ (ASA/ISO 50) which gives me an EI of 32
> with
> the same setup, chemistry, and processing.
>
> What I don't get is that all of the published data shows a higher EI
> than
> what I am getting; some times higher than what the manufacturer rated
> it at.
> Could my setup be that far off that I am loosing 3-4 stops?
>
> Scott
> smwbmp@starpower.net
>
>
>
>
> ----- Original Message -----
> From: "Greg Schmitz" <gws1@columbia.edu>
> To: <alt-photo-process-l@skyway.usask.ca>
> Sent: Tuesday, April 08, 2003 7:13 PM
> Subject: Re: Film Speed and Negative Development
>
>
>>
>> Scott:
>>
>> I don't want to rain on your parade, but it has been my experience
>> that it is almost impossible to raise the true speed of any film - no
>> matter what. I have exposed and developed hundreds, perhaps thousands
>> of rolls of test film. In reality what is usually meant by an
>> "increase in speed" is really an increase in contrast. The point at
>> which the films curve begins to pivot upward does not change, it just
>> gets steeper. I have seen minimal increases in true film speed with a
>> few special additives, pre/post-exposure, and exposing film to certain
>> gas fumes.
>>
>> Depending on what your criteria are for your negative you may well
>> find that your final results are lower than that stated by the
>> manufacturer. I base my film tests directly on the requirements I
>> have for a given type of positive and frequently rate the films' speed
>> differently for the process that I am using to produce the final
>> positive. My standard exposure for Tri-X 135, for example, is usually
>> either 200 or 320.
>>
>> -greg schmitz <gws1@columbia.edu>
>
>
>
--------------
Tom Ferguson
http://www.ferguson-photo-design.com
This archive was generated by hypermail 2.1.5 : 05/01/03-11:59:54 AM Z CST