Hi, Moose and all.
>>>it happens that the switch in styling from silver nose to
>>>black nose roughly coincided in time with the optical switch to
>>>multi-coating.
[snip]
>My very brief comment was meant to supplement the eSIF page I posted a
>link to, not to stand on its own. My point, made much clearer in the
>heading I reference in the eSIF page, was that the 2 events overlapped
>on a lens by lens basis, but were not related.
OK, it seems I misunderstood your posting. The eSIF page you referred makes
a perfect point on this.
>That's what you are
>saying, too, but in such a way that it sounds like I was not.
I beg your pardon if my posting didn't sound as I intended -- just tried to
avoid any misunderstanding.
>>Judging SC/MC by looking at the colours of the reflections is NOT easy.
>>*Theoretically*, SC reflections bear 'secondary' colours (purple,
>>yellow-gold, light blue) and MC reflections show 'primary' colours (deep
>>blue, red, green). BUT if you see together the, say, red reflection on a MC
>>surface with the green reflection of another MC surface, you'll get a
>>*yellow* reflection, usually associated with SC
>>
>No. First, the 2 reflections will appear as different sizes. Second,
>they will appear at different depths, meaning they will move relative to
>each other as the angle at which they are viewed changes.
I agree with you. At *first glance* this may look like the
"typical-SC-colour-glow", but detailed examination will reveal the
individual reflections. However, we seem to agree that, in practice, both
SC and MC lenses may show a wide range of colours -- not exclusive in any
way.
>>... Plus, the colour of these reflections may shift depending on the angle.
>>
>Not in my experience in spending too much time gazing deep into lenses
>looking at reflections.
I have to disagree respectfully here... maybe it's related to the specific
coating formulation/process or the shape of the lens, but I can certainly
see it on (ahem) Nikk*r lenses and Hoya 'HMC Super' filters -- typically
from dark green/blue to light pink/magenta. Our beloved Zuikos seem to be
less prone to this shift, however I can check this issue in some of them --
although much harder to see than the aforementioned glass, and only on
certain reflections. Now, the results of my 'research': (AKA complete waste
of time, I know ;-)
S-Zuiko 35-70/3.5-4.5 (blue->pink->yellowish white)
Zuiko 40/2 (dark indigo->pale green->pale magenta, plus the typical
green->magenta)
G.Zuiko 50/1.4 Silvernose (purplish->gold)
Zuiko 50/1.4 >11xxxxx (dark grey->green, difficult to spot)
Zuiko 50/3.5 (dark green->purplish [front] /pink [rear])
Zuiko MC 85/2 (dark green->purplish [front]->olive [rear only])
>I believe, based on empirical experience, that most of this reflection
>'knowledge' is inaccurate speculation.
I completely agree with you here...
>The marked difference between SC and MC was not color,
>but brightness. The MC reflections were much less bright than the SC
>reflections.
Absolutely. That's the point of MC -- to *reduce* the amount of undesired
flare *thru* the lens, not to show fancy reflections *on* it.
I once was with a friend (a newbie to this beautiful OM-world) who had his
MC 50/1.4. I carried my Silvernosed 50/1.4 instead, and he was amazed at
the much brighter reflections on mine.
>Yes, green and magenta
>reflections exist in some SC lenses.
I believe the theoretical primary/secondary approach is constructed around
the assumption of coating's transmittance peaks closely matched to the
most sensitive wavelengths of the eye's receivers -- this is not
necessarily so.
I've got a Soviet-made lens from 1958 (37mm F2.8 'Mir-1' -- I'd bet my neck
this is *not* MC!!!) showing some 'never-seen-on-SC' colours (dark blue and
'Kodachrome' red, IIRC)...
>In the case of the design of a lens before MC,
>the designer would still want to balance the color response of the lens.
>If all surfaces were given the same coating thickness, the lens would
>have significantly higher transmittance around the color most effected
>by that coating thickness, resulting in a lens with unnatural color
>balance. Would not the designer use different thicknesses of coating on
>different surfaces to achieve a roughly balanced transmittance across
>the visible spectrum?
Most likely. BTW, I'm amazed at the surprisingly uniform colour rendition
of my (not so many) Ze*ss lenses, even though reflections look quite
different in them.
>It is further true that individual MC coatings are not equally effective
>across the whole spectrum. A 2 layer coating can only be even
>theoretically fully effective at 3 wavelengths, and possibly only 2 in
>many actual applications. So MC lenses continue to have multiple
>different colored reflections.
This is going a bit beyond my knowledge, but I think the theoretical
approach is based on 2 fully effective wavelengths for MC.
Again, the *real* goal of all this (and I think you'll agree with me) is to
get the best protection against flare, no matter the kind of coating. This
said, I'm happy with flare-performance on most of my SC Zuikos (the 135/3.5
being an exception) -- though no coating can beat a proper hood or, best of
all, a strategically placed hand! ;-)
All the best,
...
Carlos J. Santisteban
<cjss@xxxxxxxxxxxxx>
<http://cjss.galeon.com>
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