Liam Lawless (lawless@vignette.freeserve.co.uk)
Tue, 06 Apr 1999 03:07:21 +0100
Hi Hamish,
The obvious answer about orange safelighting is that it depends on the
intensity and the length of exposure, but you don't say whether your
darkroom-mate used lith for high contrast or continuous tone, and this will
make a difference. With high contrast (i.e. developed with a lith
developer), the film is essentially either black or clear; areas of the film
that receive more than a certain amount of exposure develop to opaque black
while those areas where the exposure is below this threshold do not develop
any density. Unsafe safelighting may lower the threshold as far as the
exposure by the enlarger is concerned, but it will not show itself as fog
unless it is so bad that the whole sheet develops to blackness.
But continuous tone is different, and even a red safelight that is too
bright/too close can cause problems (as can the swing-filter under the
lens). You can easily test with coins on the unexposed film for different
times, but orange is best avoided for continuous tone on lith, or other
sheet films. If you have only orange lights, take a desk lamp into the
darkroom and fit with a 15W red Pigmy bulb (that's 15W here where we have
240v mains) and set it about 8 feet from where you handle the film. Once in
the developer, film becomes much less sensitive than it was before.
If you don't have Pigmy bulbs out there, I can send one for £300.
Liam
This archive was generated by hypermail 2.0b3 on Thu Oct 28 1999 - 21:39:30