Archived posting to the Leica Users Group, 2000/01/24

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Subject: Re: [Leica] B&W filters
From: Martin Howard <mvhoward@mac.com>
Date: Mon, 24 Jan 2000 03:45:02 -0500

Chandos Michael Brown wrote, in part:

> To pose a completely naive question:  what're the effects of filters on
> C-41 process B&W emulsions?  I looked at Kodak's tech info on T400CN and,
> unless I'm missing the obvious (always possible!), couldn't find any
> discussion of this.  Does one treat them as though they were ordinary B&W
> emulsions?
> 

I don't have Ilfords PDF datafile on hand (hmm, thought I'd downloaded
that...) but as far as I recall, their spectral sensitivity is sufficiently
similar to that of regular modern B&W emulsions that you simply treat them
as equal.  In other words, filters will have the same effect on C-41 process
B&W films as they will on regular chemistry B&W films.

A possible word of caution: while the effects on rendering tones will be
similar to B&W films, it is possible that the filter *factors* (i.e.,
changes in exposure necessary) vary slightly.  Yeah, I know that this sounds
contradictory to the stuff above, but I've got this little warning bell in
the back of my head, so it might be worth checking out.  Shouldn't be by
much though, and exposure lattitude of the films will probably even things
out.

M.

- -- 
Martin Howard                     | "Very funny Scotty.  Now beam down
Interactive Systems Designer      | my clothes."
email: mvhoward@mac.com           |
www: http://mvhoward.i.am/        +---------------------------------------