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Re: [OM] Infinity Focus problem - 55mm f1.2

Subject: Re: [OM] Infinity Focus problem - 55mm f1.2
From: Mark Dapoz <md@xxxxxxxxxxxx>
Date: Thu, 10 Jul 2003 00:37:17 -0400 (EDT)
On Wed, 9 Jul 2003, Donald Shedrick wrote:

> I just acquired a Zuiko 55mm f1.2 silver nose.  It is a beautiful
> piece of glass and in near mint condition.  But I have noticed that
> when focusing on a distant object (~couple miles) I can't quite get
> it in focus - I need to rotate the focus ring slightly more beyond
> the infinity mark, which of course it cannot do as it stops at
> infinity.  It is a very slight amount off, and only detectable with
> the varimagni finder at 2.5X and the split image focusing screen.  I
> probably only need another couple of degrees of rotation of the focus
> ring. Since I intend to use this for astro photography, sharp
> infinity focus at wide open aperture is important.  I have not got
> any shots from the lens developed yet.
> Is there an adjustment for this?  There are some small screws under
> the rubber focus ring, but I would not want to mess with them without
> knowing what they do.

Yes, just loosen slightly the three set screws under the focusing grip and
reposition the ring so that you can get proper infinity focus.  You may even
want to set it so that it goes slightly beyond infinity so that you can
compensate for temperature differences (although with a 55mm I don't think
temperature will have an effect).  You can find the parts diagram for the 55mm
lens here: http://olympus.dementia.org/Hardware/PDFs/55mm_f1.2.pdf  It shows
how the lens is assembled.
                                -mark



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