Archived posting to the Leica Users Group, 1999/09/26

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Subject: Re: [Leica] Re: Low Pressure Sodium
From: "Anthony Atkielski" <anthony@atkielski.com>
Date: Sun, 26 Sep 1999 12:23:51 +0200

From: Andrew Nemeth <azn@nemeng.com>
Sent: Sunday, September 26, 1999 09:34
Subject: [Leica] Re: Low Pressure Sodium


> Much to my surprise, found that when I scanned the
> film (C41 Kodak PJ100) that there was way too much
> colour (blues & greens)!!!

Discharge lamps are never truly monochromatic.  LPS has a very bright yellow
line that pretty much blows away everything else.  However, with a filter,
chances are that you completely removed this line, leaving only the remaining
lines closer to the shorter end of the spectrum.  As a result, you got bluish
green, instead of something correctly color balanced.  I daresay that your
exposures were a lot longer, too, no?

This is why discontinuous spectra usually require custom filters.

  -- Anthony