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Re: [OM] TTL versus OTF

Subject: Re: [OM] TTL versus OTF
From: Kennedy <rkm@xxxxxxxxxxxxxxxxxx>
Date: Thu, 30 Apr 1998 18:57:22 +0100
In article , PCA Cala <PCACala@xxxxxxx> writes
>Hi Joel:
>
>> Ok, I'll bite. What's the scuttlebut on film surface reflectance?
>
>Beats me.  I figured we would hear from those even more technically oriented
>than I.  I know that when the OM-2 came out, one American photography magazine
>rasied the question of variation in film reflectance.  It was determined that
>most were very close in reflectance and only a few special purpose emulsions
>were outside that tight range.  It probably included something like Kodalith.
>I've never seen the issue raised again.  Maybe it is worth exploring with
>today's emulsions, maybe not.  I'm too lazy to do it.
>
I remember those discussions in many of the magazines, in particular one
which suggested that it might be a problem if Ilford ever developed a
Cibachrome-type film emulsion, which is pretty much black!  It never
became a significant issue because there was no substance to it, and
pretty soon other manufacturers stopped knocking it and copied the idea.
Immitation is the sincerest form of flattery!

I did have a discussion on rec.photo.equipment.35mm back in December
last year with a Norwegian who claimed that he had measured variations
between film batches (!) that accounted for +/-1 stop exposure error at
the extreme and +/- 1/2 stop on average.  These were within the same
film stock and he had measured more than that between film types!
Apparently he had been given the job of 'calibrating' all of the cameras
used by a major newspaper chain in Norway, so he had done a lot of
tests.  I am sure the discussion is available in DejaNews for anyone
interested in reading it.

I questioned his experimental technique, since I have never experienced
an exposure change that much between actual and indicated on any film
type, so I think his errors were due to other factors.  I would be
surprised to see an exposure error of more than quarter stop between
actual and indicated due to the reflectance of the film, even back in
the days when I worked as a press photographer and took thousands of
pictures a week.  A +/-1 stop error between batches of film would have
been totally unacceptible, but my OM-2 gave equally consistent results
whether in manual or auto, colour or monochrome.
-- 
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers         (replace 'nospam' with 'kennedym' when replying)

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