Re: question about ISO vs EI

[George L Smyth <glsmyth@xxxxxxxxx>]

--- "Christina Z. Anderson" <tracez@xxxxxxx> wrote:
>       How does the EI relate to this suggested ISO; 

It does not.  EI stands for Exposure Index, whereas ISO is an international
standard.  A while back a standard was sought for informing people what speed
film was designed to be shot.  A specific developer was used and the gradient
curve established the film's speed.  This became the ISO standard.

Unfortunately, nobody uses this developer, so the information was not as useful
as it could have been.  This is why, for instance, hardly anyone shot Tri-X at
its rated speed, but cut the speed in half, as they were using a different
developer.  As a matter of fact, Kodak has completely dropped references to ISO
with their TMax series and you can shoot the film pretty much as the speed
indicated.

Exposure Index refers to the speed that you have determined proper for the film
that is shot in your camera, metered by your meter, and developed with your
choice of developers.  Your Exposure Index may (and probably is) different from
someone elses.  This is why when discussing film speed, I make reference to EI
and never ISO.

As far as the 120 version of Konica is concerned, when metered through a #25
filter and developed with Rodinal, I shoot it at around EI 10, depending upon
the scene.  You should run your own tests to determine how best to shoot this
film with your equipment and developed with your developer to obtain the
results that you are desiring.

Cheers -

george

=====
Handmade Photographic Images
http://members.home.net/hmpi/

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