In article , Jim Terazawa <jimt@xxxxxxxxxxxxxx> writes
>Dan,
>
>I think Lars Bergquist gave you satisfactory answer. However,
>I am not sure how to identify that you have LINEAR or CIRCULAR
>polarizor from your post. I have two circular polarizors - one
>by Hoya and other one by Kenko brands (both glasses are produced
>by Hoya glass - which is a separate subject). The reason I can
>tell they are circular pol is that they are inscribed "PL-C" on
>the rotating collar (also they came with little 'instruction
>manual' such as explaining how to use "V" triangle marker on
>the collar - sorry I don't have the manual with me).
>
You can tell the difference between a circular polariser and a linear
polariser by placing one in front of the other, looking through the
combination while rotating the filters relative to each other. Make
sure they are arranged in the same orientation as they would fit on the
camera.
If the image darkens almost completely and then lightens again as the
polarisers rotate, the one in front (ie. farthest from your eye) is a
LINEAR polariser. If there is almost no change in light intensity, the
one in front is a CIRCULAR polariser.
To test the filter at the back, just put it in front of the other
filter.
The slight change in light intensity with a circular polariser is
because some of them can output slightly elliptical polarised light, but
usually you can barely notice this.
Beware, if you fit the circular polariser backwards, then it will behave
as a linear polariser. So, for the test above it is important that the
polarisers are viewed in the same way that they fit on the camera - with
the side that mountson the lens closest to your eye.
Hope this helps you test which are circular and which a linear
polarisers.
<PvT>
You might like to do a search on DejaNews for "linear AND circular AND
polariser". About 100 recent articles are there which address the topic
- with a few quite detailed ones.
</Pvt>
;-)
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
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