Joe Gwinn wrote:
I just tried a simple experiment on a 55mm f/1.2 MIJ Zuiko.
All Zuikos are made in Japan and so marked. The vast majority are marked
on the side of the mount near the rear. The only time "miJ' (reflecting
the capitalization in the marking itself) is meaningful in describing a
Zuiko is in the case of the last version of the 50/1.8. In this version,
the serial number was relocated to the mount, swapped with the 'made in
Japan' notice, which moved to the front ring. These are referred to as
50/1.8 miJs as the most convenient way to distinguish them from earlier
versions. By referring to a 55/1.2 as 'MIJ', you cause confusion as to
whether the later reference to a 50/1.8 MIJ actually refers to that last
version of the 50/1.8 or some other version.
I also tried the same experiment on a 50mm f/1.8 MIJ Zuiko. The reflections in this lens are all kinds of colors, including white.
Not surprisingly, the more expensive lens (55mm f/1.2) has almost all green
reflections, and the same shade of green at that (showing tight process
control), while the cheaper lens (50mm f/1.8) has all colors (looser process
control) including white (uncoated surface?).
Assuming this is actually one of the last versions of the 50/1.8, it's
coatings are considerably more sophisticated than those on a 55/1.2, as
it was designed much later than the 55mm, at least 10 years, during a
period when the development of coating technology moved rapidly. The
original 50/1.8 was a so-so lens developed in roughly the same
time/technology frame as the 55/1.2. The 50/1.8 went through several
versions covering the whole range of OM lens development. The 55/1.2 was
apparently never changed to MC, instead being replaced with the 50/1.2.
Compare a 50/1.2 and a late 50/1.8 and I'll bet you find very similar
reflection colors.
I agree with Lee about the impossibility that this is a matter of poorer
process control on the less expensive lenses. As to the multiple color
business, I quote myself:
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"I've heard lots of people refer to the colors of the reflections, as
though the presence of several different colors shows MC. I don't see
why that would be true. 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? Of course, they must have done so based on the
color characteristics of the lenses produced. Since the color of the
reflection from a SC lens surface is determined by the subtraction of
light around the effective range of the coating thickness, this results
in different colored reflections from different lens surfaces.
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.
I have gazed into the depths of at least 3 pairs of Zuiko lenses to
compare SC to MC reflections. Although there were some (surprisingly
smaller than I expected) differences in the color of the various sizes
and depths of reflections, the most noticeable difference was the
clearly lower overall brightness of the reflections of the MC lenses,
vs. the SCs."
The earilest SC lenses tend to show overall yellow reflections, while
later ones show a number of different colors. This certainly shows the
results of improvements in coating technology and sophistication, but
not necessarily in the number of coatings per lens surface."
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Moose
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