[rollei_list] Selenium Light Meters
- From: Marc James Small <msmall@xxxxxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Fri, 29 Apr 2005 20:08:19 -0400
At 01:07 PM 4/29/05 -0700, Richard Knoppow wrote:
> Beware of two problems with Weston meters: The first is=20
>that the angle of view is very wide. This may give you false=20
>readings when outdoors if you are not careful to avoid too=20
>much sky in the reading. When used for close reflection=20
>readings they are very good.
> The second problem is with older meters calibrated in=20
>Weston speeds. While these translate to the next higher=20
>ISO/ASA speed the calculator seems to have been designed to=20
>remove a safety factor in the speeds. I have several Weston=20
>meters all with good cells. All underexpose if the Weston=20
>equivalent of an ISO speed is entered.=20
Richard
You are apparently too young to have been properly trained on selenium
meters <he grins> , but the proper method is to wave them around a bit to
obtain an average. I worked political events in the dark ages, and, as
late as 1968, we still had the Speed Graphic dudes there waving their
meters around. =20
Weston speeds are effectively .8 ASA. There are a gazillion warnings to
CALIBRATE YOUR OWN FILM!!! from all sources but I have yet to find a
single film which does not properly respond when the adjustment is made.
(That is, 400 ASA is 320 Weston).
Selenium meters are the closest match to the light response of chemical
film, and so selenium meters deserve great respect. They can be a huge
pain in the butt to use but, in the end, they will produce a more accurate
result than will anything else.
Marc
msmall@xxxxxxxxxxxx=20
Cha robh b=E0s fir gun ghr=E0s fir!
NEW FAX NUMBER: +540-343-8505
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