Re:Critique on infrared article and more questions

[HypoBob <hypobob@xxxxxxxxxxx>]

> Christina,

As for the 15, 25, and 29 filters used with Konica 750nm IR film, there is a very
slight difference between the 25 and 29 since the 25 cuts off at 590nm and the 29
at 600nm.  This difference may not be noticeable in a final print and may be offset
by the differences between filters made by different manufacturers.

The 15, an orange filter, produces the same result as a 25 with Konica 750nm film
because the filter is allowing though some wave lengths starting at about 505nm
that the film can't "see" anyway.  Your meter, if metering through the filter, will
see it, but the film won't.  (I once saw a recommendation in a book to use the
orange rather than the red filter with this film in order to gain a stop in
exposure.  A look at the film's bi-modal sensitivity curve points out the book's
error faster and easier than testing does.)

As someone else has pointed out, Rodinal is an excellent developer for the slow,
fine-grained Konica 750nm, especially in the 120 size.  Depending on your taste in
contrast, you might want to use Rodinal at higher dilutions (e.g. 1:100) to keep
the contrast to your liking.

Bob



> ------------------------------
>
> Date: Thu, 26 Oct 2000 13:47:02 -0600
> From: "Christina Z. Anderson" <tracez@xxxxxxx>
> Subject: critique on infra article and more questions
>
> Thanx for the interest in critiquing my infrared article.  I received about
> 25 requests for it (was very surprised)(whew) and have received back about 4
> critiques of it.  Please continue to send me back your input.
>      Bertha raised an interesting question.  Does putting a red filter on
> your lens INCREASE the amount of infrared light available to the film?  From
> what I understand of filters this is not so, it just decreases the visible
> light it blocks.
>      Is there truly no difference with Konica with the 15, 25 and 29 filter?
>      Do fluorescent lights in the darkroom that take a while to subside
> truly not fog infra film if you turn them off and immediately start
> developing, e.g. in trays in the dark?
>      Should I not even recommend Rodinal as an infrared developer because
> the grain is golfball size?
>      It is so nice to have you experts here to bounce these concerns off of.
> I do not want to xerox these notes for 40 students if there is wrong info on
> them.
> Chris
>

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