John Hermanson wrote:
> At least the plate has 3 screws holding it all together when you drop it back
> in. That is what tipped me off that the 35-105 zoom is definitely not
> Olympus built. The only screws holding all the blade parts in are
> the 3-4 screws that hold the blade assembly into the barrel. You have to ...
>
I'm certainly in no position to argue with your expertise. I did make a
modest effort (i.e. no tear-downs) to check the persistent rumor that it
was a version of the similar spec Tokina. Here's my list of comparison
points:
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"I can see where someone could at a casual look think they might be the
same underneath. They are very similar in size, weight and overall
appearance except for very different rubber focus/zoom ring covers. On
closer inspection, I note the following:
1. Coating reflections are different colors, indicating different
coating design/technology, and size/depths, indicating different
internal element shape/configuration.
2. Front mounting of the front element of the zooming group is slightly
different.
3. The Zuiko focusing helicoid takes considerably less rotation of the
focus/zoom ring to get to its
minimum of 1.5m and than the Tokina takes to go to its minimum of 1.6m
4. Zoom ring travel from 35-105mm is 20.8mm on the Zuik and 20.6mm on
the Tokina.
5. Although the close focus mechanism uses the same principle of acting
as an extension tube, the ring moves in opposite directions on the 2
lenses, locks into CU position on the Zuiko, but not on the Tokina and
has a different extension length, 6.6mm on the Zuiko and 8.3mm on the
Tokina.
6. Both have 6 blade diaphrams that point their fingers clockwise, but
they are mounted opposite ways, with the fingers on the Zuiko toward the
front and the Tokina to the back. The Zuiko hexagon is also a bit more
symmetrical and consistent as it is stopped down.
7. The rear element of the Tokina is considerably larger and mounted
into its cell differently than the Zuiko.
8. The finish of the visible part of the mount is classic Oly matte on
the Zuiko and shiny on the Tokina.
9. The mechanisms that convey aperture setting to the pin on the rear
and operate the diaphram from the other pin on the rear are quite
different designs, with the Zuiko using the same basic design as in
other Zuikos I've had apart.
10. The Zuiko has 16 elements in 12 groups and the Tokina has 16 in 13.
11. Ths Zuiko is styled pretty much like the 70-150 and 35-70/3.6 &
35.-4.5 except fot the close-up ring, which isn't on those zooms, but it
is in the same relative position as the zoom rings on those 2 touch
models. I assume the otherwise odd design of the CU ring with the groove
around the middle is to differentiate it from the zoom rings on the
others. The Tokina is styled just like the other Tokina zooms I have.
Finish of the body surfaces is very similar.
12. The nose of the Tokina in front of the zoom ring is much shorter
than on the Zuiko, so the Oly hood doesn't clamp on as securely. The
Tokina hood is also a clamp-on design but is calculated for use with a
filter and uses something like an empty filter ring for the hood to
clamp onto when a filter isn't. The Oly solution of a clamp on hood that
doesn't interfere with filter use is much nicer.
My conclusion? It is extremely unlikely that the Zuiko is an adaptation
of the Tokina. There are just too many differences that wouldn't make
sense if it were, especially things like reversing and changing the
length of travel of the CU helicoid, changing the pitch of the focusing
helicoid and changing the internal design of the auto aperture
mechanisms. It also really does appear to me from the reflections that
the internal elements differ quite a bit in surface curvatures and/or
locations."
Moose
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