From: "Richard F.L.R. Snashall" 
To:  atm{at}shore.net
Reply-To: "Richard F.L.R. Snashall" 




John Sherman wrote:
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> Hi Tom, Hi James, everybody,
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>>Check out these essays (at bottom of page)
>>http://voltaire.csun.edu/roland/index.html
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> Maybe Ohara's values assume an anti-reflection coating? Does anybody know?
> I'm sure it is not strictly true that "all refractors are in the 88 to 90
> percent range." Yet Roland does not quote any throughput values.
>

The catalog transmittance values are for once the light gets into the
glass.  IIRC, they are measured by adhering the measurement equipment with
fluid.  This method produces a very low reflectance.

However, the "color code" values include the value lost via
[normal] reflectance.  For some glasses, the color code goes awry, as the
index is so high, they can't get 80 percent through the material.



                Rick S.

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