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Re: [OM] Oily 300/4.5. Suggestions?

Subject: Re: [OM] Oily 300/4.5. Suggestions?
From: John Hermanson <omtech1@xxxxxxxxxxx>
Date: Thu, 04 Jun 2009 09:04:12 -0400
I agree.  OM-2000 is metal body casting, Cosine badged version is 
plastic body.
___________________________________
John Hermanson  |   CPS, Inc.
21 South Ln., Huntington NY 11743
631-424-2121  |  www.zuiko.com
Olympus OM Service since 1977
Gallery: www.zuiko.com/album/index.html


Carlos J. Santisteban wrote:
> Hi John, Chuck and all,
> 
> From: John Hermanson
> 
> 
> 
>> I've seen Cosina lens quality and FWIR (from what I recall) it's not even
>> close to 35-105 quality. I have always thought Tokina.
> 
> 
> Most likely. Cosina branded lenses were usually aimed to the
> amateur/entry-level.
> 
> However, Cosina has made bodies and lenses for many brands, with huge range
> of quality. For instance, I've seen inside a Cosina-made Y*shica FX-3 (which
> is a rather reliable little beast) and a 'Centon' camera -- essentialy an
> FX-3 in K-mount. But build quality had nothing to do with the Y*shica,
> despite both coming from the same maker.
> 
> Cosina is currently making some fine rangefinder lenses under the
> Voigtländer brand, although some of the older Bessa bodies had a toy-like
> build quality :-(
> 
> BTW... I have ordered from S. Gandy an Ultron 28/1.9 in LTM. Next purchase
> (as money permits!) will be the 21/4... and the 40/1.4 in Leica-M mount
> should follow ;-)
> 
>> Oily diaphragm may eventually spray a fine coating of oil all over the 2
>> elements that face it.
> 
> That is a real risk, although probably only in extreme cases. Another risk
> may be internal flare caused by the reflection on the shiny oil instead of
> the dark matte blades...
> 
>> From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>I think Carlos is wrong
> here.
> 
> I may be wrong, of course. I haven't taken apart any Zuiko (safe for
> removing a dead bug from a silvernosed 50/1.8!!!) and internal layout of
> mechanics may vary depending on the particular model.
> 
>> He implies there is a direct mechanical
>> connection to the blades
> 
> However, I have repaired several OT lenses with oily diaphragms and direct
> connection to the blades was definitely the case there, so I assumed Zuikos
> would be the same.
> 
>> when closing down such that oil can't cause
>> problems on closing but there is only a weak spring on return which can
>> lead to sluggishness with oily blades.
> 
> Again, most OT lenses are "normaly closed", so the weak spring is the
> responsible for that, and may suffer from oily blades. But Pen-F lenses are,
> like OM, "normally open" and I have seen at least one of these which didn't
> close in a timely manner... it may depend on internal construction, really.
> 
>> As your comment below makes
>> clear ("shutter fires but does so without the blades stopping down")
>> that can't be the case.
> 
> I think the key here is what followed that John's quote:
> 
>> (that's an extreme case)
> 
> Of course, I can only speak from my experience, but have checked again the
> 50/1.2 @ OM2 (which doesn't show oil in the blades that I can see, but has a
> rather stiff auto-diaphragm pin -- maybe is a completely unrelated fault?)
> and, when "releasing the shutter" (i.e. pushing the button) it takes about
> half a second for the blades to close, and *then* (already at the proper
> shooting aperture) the shutter actually trips (checked also by looking from
> the back of the camera, open without film).
> 
> So I'd like to raise a question... how many of us had overexposure problems
> _actually_ related to a sluggish diaphragm, and with which lenses? Please
> note that my "theory" won't apply to the OM-2S, PC and 40, because of the
> different diaphragm action. Another possible, unrelated problem is in
> _manual_ or spot mode, when an oily iris won't open completely after
> exposure (that's the behaviour of my 300/4.5, BTW) throwing off meter
> readings somewhat. Won't affect OTF, though.
> 
> It's really nice to learn so many things on this list...
> 
> Cheers,
-- 
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