Re: Konica base fog

[HypoBob <hypobob@xxxxxxxxxxx>]

>

Stan,

Konica 750 does have higher base density than most 120 format films.  It always takes about one
stop more exposure for the contacts.  I have shot refrigerated Konica 750 that is over two years
out of date without any noticeable degradation.  (Of course in the world of IR since one never
knows exactly what to expect, it is hard to be disappointed.)

The orange filter does allow additional light through the lens, as compared to the 25A, but it
is light that Konica 750 does not "see", so you get no benefit in terms of film speed or
additional tones in the negative.  Konica 750 has a bi-modal sensitivity curve with one peak in
the blue to blue-green region and the other in the red to near infrared.  The orange filter is
passing some wave lengths between those two peaks where the film sensitivity is zilch.

Bob

----------------------------
Stan Patz wrote:

>
> To the group,
>
> I just ran some Konica 750 tests in a new 120 rollfilm camera. I processed
> similar rolls of film in D-76 1:1 for 8min @ 68*F, and Rodinal 1:50 for
> 7 min. Both rolls looked good - images came out with the same film speed! But
> both rolls showed fairly high base fog; slightly grey. Is this usual, or a
> problem with 1yr outdated, but refigerated film.
>
> For the tests, I used a 25a filter, and got good results. On a few frames, I
> used a Tiffen "orange" filter, but got no speed increase over the 25a.
>
> What is the Wratten equivalent to the Tiffen filter, and has anyone found
> and advantage to using it over the 25a?
>
> Stan Patz   NYC
>
> SKP113@xxxxxxxxxxx
> www.PatzImaging.com
>

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