Would your friend and colleague, Doug, know that? I have done a lot
of that type of photography over the years but never considered the
fact that magenta is not a naturally occurring color. Next you'll
tell me cyan doesn't exist either.
Don
ADavidhazy wrote:
I am trying to prevent making a total ninkompoop of myself (yeah, I know it is
too late for that!) and so I need some advice/information on the color seen in
a typical stress analysis polarization set-up. Two linear polarizers generally
at right angles to each other with a birefringent material (cellophane,
stressed plastics, etc.) in between. Under such conditions colors are seen.
Explanation? Especially as concerns magenta and green. Possible explanation:
Since the spectrum does not contain the color magenta in it, then in a crossed
polarizer set up is magenta seen due to the fact that green has been
selectively removed from the incident white light beam and we see some red and
some blue passing through and thus preceive magenta?
Further, if this is so, then all the colors seen in a polarization system are
due to the mixture of those wavelengths that pass through the 2nd polarizer. In
the case of magenta both red and blue must be passing through while when we see
green then in that area green has lined up its plane of polarization with that
of the 2nd polarizer and red and blue eliminated.
So we see colors both due to subtraction of specific wavelengths and to simple
transmission of others.
Ideas? Is this correct? If not would you be so kind as to help me understand
the process better? Thanks for any assistance beforehand!
Andy
Andrew Davidhazy, Professor
School of Photographic Arts and Sciences/RIT
andpph@xxxxxxx http://www.rit.edu/~andpph
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Don Roberts ** Bittersweet Productions ** Iowa City, IA
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When our memories outweigh our dreams
we become old. -----William Jefferson Clinton
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