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[OM] Focusing a 28mm f/2.8 lens

Subject: [OM] Focusing a 28mm f/2.8 lens
From: "Jim L'Hommedieu" <jlamadoo@xxxxxxxx>
Date: Sat, 10 Feb 2001 17:54:13 -0500
Hey all,

I'm new to the group so I'll introduce myself briefly.  I'm an advanced
amateur living in a suburb of Cincinnati, Ohio (actually across the river in
Northern Kentucky) USA.  My first 35 was a Miranda Sensorex (which sported a
shutter release on the front of the right side- not on top.  It sounds
strange but it was quite natural to squeeze the body, releasing the
shutter.)

>From there, I bought an early OM-1 (before they were MD capable).  The meter
died so I bought an OM-2, used.  My favorite body though is the OM-PC
because it has LEDs in the finder which is indispensable for taking concert
pictures.  A sample photo is at
http://www.jonimitchell.com/BSNTourReports/PineKnobBSNTourReport.html
Since none of my bodies has a spot meter capability, I set the PC to
underexpose by 2/3 stop.  This keeps the subject from being a blocked up
highlight.


  I now have these Zuiko lenses:
28mm f/2.8
50mm f/1.8
50mm f/3.5 Macro
100mm f/2.8
200mm f/4

In addition I have a Sigma 400mm.  I have found the 100 to be noticeably
sharper than the rest.  The 50 normal and macro are acceptably sharp.  I
must admit though, that I've never produced a razor sharp image at any
aperture with the 28 or 200.

I asked John if he thinks that the 28 might have a repairable problem
(there's no rattle, no sign of damage, I've never dropped it) but he
suggested that it's inherently harder to focus wides especially when it's
not a speed demon like the f/2.8.  The last time I used the 28, I was in
full sunlight and chose an aperture near f/8 for maximum sharpness.  My
subject was sitting in a chair, so I had ample time to focus carefully.  I
noticed that it never "snapped" into focus.  I could turn the focusing ring
through a 2 or 3 mm arc, without the focusing screen getting any better or
worse.  I ended up centering the ring in the middle of the range of
uncertainty but the resulting 4" x 6" glossy print was just not sharp enough
to warrant an enlargement to 8x12.  I've looked at test results of this lens
on various sites and there's a variation among results.  I was considering
upgrading to the f/2 model of this focal length but apparently, the extra
money goes into a close-focusing refinement- and I don't use a 28mm at close
distance.  Anyway, do I have a poor example of this lens?  I have no trouble
focusing the 100 f/2.8 in full sunlight.  (I am 45 though, so my focusing
ability may be waning.)

Would it help to "bracket" the focus or is it just a mediocre lens?

Jim Lamadoo



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