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    Re: Polarising Filters
    From: George Huxtable
    Date: 2007 Nov 24, 00:29 -0000

    Clive's attachmenent about polarising filters raiises another aspect of
    dark-shades for the Sun, which appears not to have been touched on so far.
    
    I recall having read, but don't recall where, that simple local heating,
    from the Sun image falling on the retina, is a cause of lasting damage to
    the retina by short-term ablation. That is, it fries a hole in it. Can
    anyone offer more information about that?
    
    If that is indeed the case, shouldn't we be thinking about the infra-red
    attenuation? How can we be certain that carefully crossing a pair of
    polaroids, to minimise the light that comes through, has a corresponding
    effect on the passage of heat? How can we be sure that an ordinary dark Sun
    filter is correspondingly dark to infra-red? Have these matters ever been
    addressed?
    
    George.
    
    contact George Huxtable at george---.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
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