Friends:
I recently had a chance to submit all my Zuiko glass to the "Giles' Green
Reflection Test" to verify multicoating. (I call it the "G.G.R.T."
because it was Giles who tipped me to the fact that green or aquamarine
reflections in a lens made it somewhere between highly probable and
absolutely certain that a Zuiko was multicoated). Giles and I have had
some off-list conversations about this topic, and I know he is still
looking, in the best scientific tradition, to see if he can *disconfirm*
the hypothesis that "green means it's multicoated." All my lenses conform
to the G.G.R.T. rule; the presence of green always indicates
multicoating, as verified by 1) MC inscribed on the lens, 2) the obvious
recent manufacture of the lens, and/or 3) the MC designation at the
Hawkins website, which appears to have correctly identified the SC/MC
status of every lens I own.
HOWEVER, I have one lens, a 50mm f/1.4, serial number 9001XX, that
doesn't support the *reverse* of the hypothesis, which would state, "All
MC lenses show a green reflection." (Logicians: isn't this reversed
hypothesis called "affirming the consequent"?) The lens I mention is
clearly marked MC around the objective, yet I find no green reflections
on any of the surfaces, after exhaustive viewing in a variety of light
sources. I see lavender, rose, pink, but no green. Well, with one tiny
caveat: if I hold this lens just right, I am able to view a
lighter-colored ring deep within the lens. As I move the lens slowly in a
strong light, I can view a 'refraction rainbow' against this lighter
surface -- and, like any "rainbow refraction," there's a tad of green in
it. But this lens does not demonstrate the obvious "green (or aqua) light
bulb" reflection that I'm accustomed to seeing in other MC lenses, when
examined under a strong bare bulb.
I'd like to hear others verify this before I declare, positively, that
"green always means multicoating but multicoating doesn't always mean
green," but I believe I now have some evidence toward this statement.
================================================================
Kelton Rhoads, Ph.D. kelton@xxxxxxxxxxxxxxxxxxx
================================================================
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|