From: Yu rei (nanocrystals2003@yahoo.co.jp)
Date: 09/12/03-01:45:15 AM Z
--- Katharine Thayer <kthayer@pacifier.com> wrote:
A thing can't be both transparent and opaque at the same
time.
True, perhaps, if you are discussing the same wavelengths!
But,
It CAN have a value represent it's transparency and a
value represent its opacity, whatever those values are.
>density is a separate issue from opacity.
No.
Sorry for jumping in here because I will jump out just as
quickly... It is not that I disagree with what you want to
say, but just the following two points woke me up! This
'back and forth' reminds me that Density and Transparency
and Opacity are not 'all or nothing' absolutes.
Katherine, I belive, is limiting her language of the use
of "Opaque" (100% opacity) whereas the other person is
not.
This is permissible because of the following reason.
I belive that Photographic Density (D) ranges from 0 to
about 4 and is defined as the log of the Opacity (O).
Opacity here being defined as the reciprocal of
Transmission (T).
What this means is that if 500 photons of light fall on a
filter, and 250 pass through, the filter would have a
transmission of 0.5 or 50%; The opacity is 2 and the
density: 0.3 or such as to provide a one stop loss of
light.
Ray
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