Philip Pemberton wrote:
>Hi,
> I've just got my holiday photos back, and I've noticed a bit of a problem
>on most of the negatives.
> All of the photos I took where the subject was between 4m and 10m away are
>hopelessly out of focus, even though they appeared to be perfectly in focus
>in the viewfinder. I didn't use the prism or "image slicer" focus aids,
>because they don't seem to work very well on my OM10 for some reason
>(especially in very light/very dark conditions). Aperture was full-open (f1.8
>for the shots taken with my Zuiko 50mm, f4 for the ones I did with the Tokina
>80-200) due to low light conditions. Most of the time, the exposure metering
>came up with stupid figures (1/250 in the middle of a dark woodland area, I
>think not) so I set the camera on 1/60. Camera is an Olympus OM-10 with
>Winder 2 (I want an OM2sp!).
>
>
So I assume you already know your exposure meter is wonky. One possible
cause of focus trouble that's apparent only at wider apertures is a
mirror that is out of adjustment. DOF can mask the problem at smaller
apertures.
>I've uploaded some of the photos to
><http://www.philpem.castlecore.com/gallery/> (in the Scotland album), with
>more to come just as soon as my Epson 2400 scans them and I tweak the colour
>correction a little. I really do need to get a negative scanner, but I've been
>promising myself an OM2sp for ages... hm... decisions, decisions. IMHO, 07A
>is probably the worst and 16A is probably somewhere near the best. Or rather
>it would have been if it were a little lighter, but that's more or less what
>it looked like in real life...
>
However, I don't think the mirror is the problem here, because focus is
missed in both directions. In 07a, the plane of focus is behind the
subject, with nice sharp foliage behind a fuzzy tree/box. In 10a, the
subject is still oof, but the stuff behind it is even fuzzier and the
green leaves in the sun are more in focus. So I must conclude that focus
was missed in opposite directions in the two shots. 12a looks like is is
focused just a bit behind the subject, with the branches immediately
behind the tree at least close to in focus. 13a looks like the front of
the tree itself is in focus, but the box isn't quite sharp. Very close
to correct focus. 15a is focused a little further behind again, close to
12a. 16a may be better than 13a, but it's so dark who can tell.
You say you avoid using the split image focus aid. Do you simply focus
on something outside the aids while keeping the framing you want to
shoot? If so, you may be focusing on something at a different distance
from the camera than the subject. At f1.8 and 50mm or f4 and a longer
fl, that's not going to work because of the shallow DOF. I can see how
it would be difficult to focus on the subject here in dim light and
easier to focus on the clearer, back lit detail of its surroundings.
Those visually surrounding objects are all behind teh subject all but
one shot are focused behind the subject. If your main subject is in the
center and you want to use the matte area to focus, you need to get the
subject out from under the focusing aids, focus, reframe and shoot.
With a some of sharp edges on the box, I would think the split image aid
would work properly here. I suggest some tests with a cheap roll of
film. Try focusing on something with split image, take a wide open pic,
note the distance on the lens scale, then try slightly different focus
settings in both directions. Then do the same thing focusing using the
matte area. Keep careful notes, or it will all be a muddle when you get
the results back. That should determine whether one or the other or both
are accurate and, if not, in which direction the inaccuracy goes.
If the results show a problem with focus in the camera, replacement is
probably better than repair, with an OM-10. If the results show that the
focus is accurate in good light with a target selected to be easy, then
the problem is in your focusing technique in the field and an OM-2sp
will have the same problem. If the tests show that the focusing aids can
be relied on for accurate focus, you can use them in difficult
situations like the samples you posted. It's really hard to accurately
focus on the matte surface in very low light.
Moose
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