[LargeFormat] Shooting LF in below freezing conditions

[Richard Knoppow]

----- Original Message ----- 
From: "Dave Hornford" <dave@qillaq.com>
To: <largeformat@f32.net>
Sent: Thursday, April 24, 2003 11:09 AM
Subject: RE: [LargeFormat] Shooting LF in below freezing
conditions


> Gavin,
>
> Although Uncle Dick enjoyed his formative years in a land
that has winter,
> all the time spent in a tin darkroom extension on the
sunny side (north) of
> has induced heat stress.
>
> I shoot my Sinar A outdoors in all year on the Canadian
prairies and in the
> Rockies. There are a wide range of cold issues. Based on
my extensive 2
> seasons of experience I humbly offer the following notes.
>
Snipping...
> 2. Shutter reliability.
> I have a lovely Compur shutter that has been CLAed.
However, below -15 C it
> reacts unpredictably below about 1/100th. A 50th can be
anywhere from a 50th
> to 2 or 3 seconds. At -30 C it sometimes just won't fire.
Now my Copal works
> to every temperature I have tried.

   I don't know what is different in the Copal. The old
standard treatment for shutters in cold weather was to have
them cleaned and run dry, that is, no lubricant at all. It
is the lubricant getting very viscous which makes the
shutter irregular. There are modern lubricants, synthetic
oils, which maintain their viscosity over very wide
temperature ranges. They also have less tendency to get
gummy with time than petrolium or animal oils. The Copal may
be lubricated with one of these, or may simply run dry.
  If you use lenses with old large size Ilex Universal or
some Compound shutters be aware that the shutter and
diaphragm blades are made of Ebonite, a type of hard rubber.
It may become brittle in very cold weather.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com