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

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Subject: [Leica] Re: Low Pressure Sodium
From: Andrew Nemeth <azn@nemeng.com>
Date: Sun, 26 Sep 99 17:34:51 +1000

> But no detail at all is rare.  Low-pressure sodium is one of the 
> few situations in which there is no detail at all.  Actually, it's 
> no so much that there is no detail, as that the detail in all three 
> channels is proportionately the same, so there are no differences 
> that can be exploited to recover actual color

In march of this year I did a VR shoot at the Australian War Memorial
Museum in Canberra.  A sequence of shots was taken at the 'Treloar
Technology centre', a huge hangar where fighter planes, tanks and
artillery are stored.

The whole place was lit with Na-lights, so everything was monochromatic
yellow.

For a lark, decided to to shoot with a 80A filter over the 90mm Sumicron
R and the 80B built-in filter in the 16mm Elmarit R.  Guessed that just
maybe the blue filter will help keep the yellow a little under control.

Much to my surprise, found that when I scanned the film (C41 Kodak PJ100)
that there was way too much colour (blues & greens)!!!  In fact, I had to 
mix a bit of yellow back into the images (via PShop) to make them look 
more representative of the actual lighting on location.

So much for Na-light being monochromatic!

The images are online at the war memorial's www site:

<www.awm.gov.au/virtualtour>

Click through to the individual scene pages, then scroll down to
the bottom to the 'Treloar Centre' stuff.

Regds,

Andrew Nemeth
nemeng.com