If it has recently been purchased with known, or undisclosed faults (the
sticky focus issue) it may have been subject to an unskilled botched repair
attempt by the seller. I know the 250mm I had for a few hours had been
abused prior to my owning it. Cambridge had not disclosed any of the issues
with that lens in their sale listing. If the scarcity of this lens is
accurate who knows the one John has been asked to work on may be the same
one I had.
The sticky focus problem could be due to a drop that put the focus ring
slightly out of round perhaps or it could have shifted the internal
mechanism somehow, remember this lens has close focus correction that moves
the internal groups as the lens focus' closer. Element reversal is a very
real possibility if an unskilled repair person was in the lens. Either way
it is likely a sad thought that this lens is probably never going to be
repaired either due to parts unavailability or fear of damaging it further.
If I was in John's shoes I know I would be reluctant to do much with it.
Dan.
-----Original Message-----
From: Dawid Loubser
Subject: Re: [OM] Separated Zuiko 250/2, was: Inside the Zuiko 300mm F4.5
Hmm - that's quite a plausible theory from an optics point of view,
would explain
why it could be sharp in the centre (where it never matters which way
around the elements
are mounted, except for coating differences and as long as the order
is maintained) and
go all screwy in the corners.
Usually element separation is plainly visible.
On the other hand, I wonder who would have the guts to take a 250/2.0
apart without him
knowing *exactly* what he was doing. Even our on-list genius John
seems scared to take
on this problem :-)
--
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/
|