Re: Kodak HIE and #87C

[Otto Giesenfeld <otto.giesenfeld@xxxxxxxxxxxx>]

--On den 20 juli 1999, 13:59 -0700 Tolga Yayalar <tyayalar@xxxxxxxxxxx>
wrote:

> I've been using #25 filter quiet while but recently I purchased kodak's
> 87C filter. I've just developed my first roll, I was shocked with the
> results. I had shot the roll on a sunny day with some clouds. In some
> shots I also used #25 filter  just to be able to compare later. The ones
> that I shot with 87C are almost completely black, I can see the image but
> they are so dense that edges of the film is effected too. But the ones
> that I shot with #25 are just as I expected. I used 400iso when #25 is
> atteched to the lens and 12 iso with the #87C. Kodak and most people
> suggest 10 iso with the 87C but my camera has 12 minumum. I also
> developed in rodinal 1+50 12min@xxx This combination gave me good results
> with #25 at 400 iso. I wonder where I did wrong. Is it the film speed or
> developement? I know IR light is very unpredictable but what is the
> filter factor of 87C? Any ideas and suggestions would help a lot. Thanks

Since you are getting good results with #25 and EI 400, I assume you use
through-the-lens metering. Kodak's recommendation for metering without
filter when intending to use #25 is EI 50, and since a red filter tends to
affect meter readings by around 3 steps, it makes sense to use something
like EI 400 for TTL metering with the filter on.

Considering that the recommendation of EI 10 for use with #87C filters is
also intended to be applied to filter-free metering, the only thing you can
conclude from it is that your exposure should generally be about two stops
longer when using the #87C than the exposure you expect to get good results
from when using #25.

Thus, forget about setting the meter to anything near EI 10 if you do the
metering with the filter on. Instead, take a meter reading of a typical
scene through the #25 filter, then attach the #87C filter instead and
adjust the EI setting of the meter until it indicates at least two stops
more exposure than it did with the #25 filter. Then use this EI setting as
a starting point for experimentation. There is no reason to be surprised if
the "correct" EI setting for use with #87C turns out to be even higher than
EI 400. The meter might be rather insensitive to the IR light that #87C
lets through and may therefore require a very high setting when used with
that filter.

By the way, what kind of equipment do you use?

Best regards and good luck,

Otto
E-mail: otto.giesenfeld@xxxxxxxxxxxx

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