[rollei_list] Re: Meters and Film
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Tue, 1 Sep 2009 14:18:27 -0700
----- Original Message -----
From: "Marc James Small" <marcsmall@xxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Tuesday, September 01, 2009 1:58 PM
Subject: [rollei_list] Re: Meters and Film
At 04:51 PM 9/1/2009, Richard Knoppow wrote:
> BTW, I disagree with the statement (which I snipped)
by
>a previous poster that film has a two stop underexposure
>latitude. When the speed is determined by the ISO method
>there is almost no underexposure latitude since the method
>is intended to find the minimum exposure that will result
in
>good shadow detail. One can underexpose somewhat but there
>will be a loss of shadow detail. OTOH, there is an
enormous
>overexpsure latitude, maybe as much as ten stops for some
>films.
I probably was the fellow to whom you are
responding. There is an Ilford technical paper
on this from the 1990's which I got back when I
was an IlfoPro member, another one from ORWO from
the 1980's (auf Deutsche, naturelment) and yet
another from Kodak which is referenced in the
Gevaert Manual of 1964. Two down and three up
for B&W was the industry standard for decades.
And my personal experience remains that with B&W
films, a two-stop underexposure will still result
in a printable image. Yes, you will lose some
shadow detail but, then, that is often a
mechanism worthy of note to bring out the primary target.
Of course, the answer was always, "bracket,
bracket, bracket". "Film is cheap, the image is
priceless", as the photo editor from the Baltimore
NEWS-AMERICAN said in 1975.
Marc
"Printable" is the key word here. If you can find them
read over the research papers by Loyd A. Jones (he spelled
it Loyd) mostly published in the journal of the Franklin
Institute. The original ASA speed standard was an adoption
of Jones' work and the current ISO standard it related to
it. The research was into the real world speed of film and
what exposure was needed to produce "excellent prints".
Jones' conclusions and assumptions about photographic
subjects were based on extensive measurements and actual
prints judged in a double-blind test. Its quite possible
that there may be criticism of the work by modern readers
but Kodak based much of their choices of film and paper
curves, etc. on this work.
Jones seems to be almost forgotten now, which I think is
unfortunate because we are still living with the results of
his research.
I will try to come up with specific citations but you
can find them in Mees' classic _Theory of the Photographic
Process_. The "revised edition" is better although I think
Jones did work even after this was published. It does have
citations to his classic work on tone rendition and
exposure.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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