[rollei_list] Re: An ebay explanation
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Mon, 19 Mar 2007 17:44:24 -0700
----- Original Message -----
From: "Marc James Small" <marcsmall@xxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>; <rollei_list@xxxxxxxxxxxxx>
Sent: Monday, March 19, 2007 1:49 PM
Subject: [rollei_list] Re: An ebay explanation
At 06:33 PM 3/19/2007, Peter J Nebergall wrote:
>Is there anyone who can recalibrate Westons that work but
aren't
>accurate?
>
Again and again, Peter:
George Milton at Quality Light-Metric in Hollywood,
California.
Marc
msmall@xxxxxxxxxxxx
Cha robh bàs fir gun ghràs fir!
FWIW, there are really no adjustments in a Weston. The
Selenium cell output depends on its size and possibly other
physical characteristics. The meters are very well
constructed: this was Weston's principle business. The
degratation of the cells is a chemical process typically
caused by moisture or heat.
Quality Light Metric sometimes adds neutral density
filters to lightmeters. I am not sure I go along with this.
The usual failure of Selenium cells is that they get
non-linear, losing sensitivity for high light levels. Since
the error is not constant there is no simple way of
correcting for it.
Another problem (I think I mentioned it before) with
Selenium meters of like the Weston and some General Electric
is that the connections to the cell are by pressure contacts
pressing on a conductive material. If the springs oxidize a
bit contact will be lost or become intermittant. The fix for
Weston meters is simple: press down on the cell window and
twist it a little. This will generally bring the meter back
to life and will cure intermittant readings, at least for a
while.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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