In article , Jim Worthington <knoxmore@xxxxxxxxxx> wrote
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>I don't know much about using polarizers with SLRs, but light will be
>polarized when reflected off a first surface mirror (like on the way to the
>pentaprism!). What you see in the viewfinder may not be what the film will
>experience. Has anyone studied this?
>
Yes, my final two year project of my Physics degree at university was
polarisation of light - its creation and uses.
Reflection off the aluminium front surfaced mirror will only produce a
small degree of polarisation (at 45deg this will be around 50r less) -
so low that it is frequently ignored and the reflected light is
dominated by unpolarised light. This is a consequence of the high
reflectivity of aluminium on the mirror - were it gold, for example,
which has a lower reflectivity in the visible band, the polarisation
would be more significant, and at 45deg incidence the reflection would
be around 300olarised.
In this case however, the light reaching the mirror is already polarised
by the filter, and linearly polarised light will become elliptically
polarised when reflected from a metal surface. Once again, however, the
difference would be small due to the high reflectance of the mirror. I
am not aware of any significant differences in the human visual system
observing linearly, circular or elliptically polarised light, so I doubt
whether such a small degree of ellipsis would cause any change in the
perception of the image.
To all intents and purposes you can ignore the front silvered mirror
from polarisation effects with one exception - the semi-silvered section
in the OM-4 and subsequent cameras.
--
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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