Jim,
First:
It is inherently harder to focus a wide because the DOF is deeper and
subject material in the viewfinder is smaller. It's a little more
difficult with an f/2.8 than an f/2 also. Try using the split image or the
microprism ring if you can. If you must err, do so on the close end, not
the far. As distance increases, the DOF behind the subject grows faster
than the DOF in front until you hit the hyperfocal distance (DOF depth goes
to infinity and DOF depth in front is half the critical focus distance).
Second:
You mentioned your eyes and that you are using an OM-2. You might explore
dioptric correction for the eyepiece. The Eyecup 2 with diopters is still
available. A number of us on this list who wear corrective lenses (for one
reason or another) use them and found they made accurate focusing much
easier. You might be surprised at the difference it makes. The trick will
be determining how much you need. Note that the magic age for reading
glasses is 40 years old. You needn't give up manual focus gear! There
have been a couple of recent threads about dioptric correction.
-- John
At 22:54 2/10/01, Jim Lamadoo wrote:
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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