I had some off-list discussion about my polarizer question with Gary Reese
which he has given me permission to post. This post was a followup to his
original message in which he said he uses a filter factor of 2 stops with
all his polarizers. Gary said the 2 stops is a sort of an average of all
of his polarizers, which vary in filter factor from 1 and 2/3 to 2 and 1/3
stops. I asked him how he determines a filter factor for his polarizers,
and that's where his response below picks up.
Joel W.
--------------- Text of forwarded message ---------------
Date: Fri, 14 Mar 2003 12:23:17 -0800
From: Gary Reese <pcacala@xxxxxxxxxxxxx>
X-Accept-Language: en
To: jowilcox <jowilcox@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [OM] Reviewing the Basics of PL's with OM-4 :::off-line:::
References: <3E7B3EF3@xxxxxxxxxxxxxxxxxxxx>
Hi Joel:
I just put the polarizer up against a hand held meter. If it is aimed at
something that wouldn't have any polarizing effect anyways, you get what the
neutral density factor is for that filter. Ansel Adams cautioned against
changing exposures just because a TTL meter changes when rotating the filter
on something which has a polarization effect. Your film will often
underexpose if you do.
There have been a few references which list the filter factors as variable
for a polarizer. Some are darker than others.
I'm very much in the camp which DOESN'T meter through any filter if I can
help it. The spectral sensitivity of photocells in cameras isn't even across
the spectrum. In particular, orange and red filters will underexpose your
shots if you meter through them. Likewise, filters under yellow rich (indoor)
light will meter differently than filters under blue rich (outdoor) light.
Carry a filter factor chart and use that for the most consistent results.
Feel free to share these comments on the OM List.
Gary
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|