Archived posting to the Leica Users Group, 1999/06/30

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Subject: RE: [Leica] Fluorescent filtration
From: "Henning J. Wulff" <henningw@archiphoto.com>
Date: Wed, 30 Jun 1999 23:38:42 -0700

Tim A wrote:

>At the risk of turning into a LF list!, check out this review of NPS.
>
>I have used the procedure Henning suggests - works well - many clients seem
>happy with LF prints from the negs, without bothering with transparencies -
>even for publication. I think there may be more of the Fuji four layer films
>available now (does Reala have this in 35mm?):

Yes, Reala (the old one) had it first in all formats, now more Fuji films
have it. They are much more forgiving of nasty colour casts than any
transparency film. The main thing is to either do the Vericolor chromes
yourself, or have someone very good do it for you. I'm lucky to have the
latter.

You can't get the same overall colour response as with daylight from any
other light source; each light source will produce its own rendition. With
tungsten or halogen lights it's possible to get close with filtration, but
there are still differences. With discontinuous spectra, like flourescents,
it's impossible to filter for similar response because no filter is an
exact inverse of the spectral differences between daylight and any given
flourescent tube. So called 'higher quality' flouresecnts have coatings on
the insides of the tubes which make them less efficient, but spread the
spectra through secondary emissions and internal filtration. Some gas
emission lights such as low pressure Sodium Vapour are impossible to fix as
there is virtually no energy in large expanses of the spectra.

In my photography, it's usually OK to photograph with the existing lights
as those are the lights that usually illuminate the rooms, so the spectral
responses are for the most part 'normal' for that room. The Fuji negative
material just allows me to correct for the human perceptual spectral
accomodation.

   *            Henning J. Wulff
  /|\      Wulff Photography & Design
 /###\   mailto:henningw@archiphoto.com
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