I believe there are at least two internal designs on the 35-105. Other
differences related to aperture and zooming were observed on the list a few
months ago (some of the postings from C.H. Ling ??). I was able to
determine that mine is apparently one of the newer ones (S/N 106###). The
image doesn't normally darken moving from 35mm to 105mm, nor does the
metering shift much. When I'm using the 35-105 (my only zoom) the camera
is usually in TTL Auto and I don't worry about it. Having used it with a
good amount of Kodachrome 64, exposure through it has been consistently
excellent under a wide variety of conditions. Thus, there's never been a
reason to worry about it.
Remember that the lens is wide open when metering in manual mode. As you
set the aperture a lever in the lens moves against another one on the body
to bias the metering. Unless this lever moves slightly as you zoom with
apertures tighter than f/3.5 (to correct the biasing), the metered reading
should change as the lens is still shifting from f/3.5 to f/4.5, a total of
2/3rd f-stops.
-- John
At 20:46 7/8/01, Parzival Herzog wrote:
A couple of days ago, I was checking my recently purchased
OM4T meter against my OM2n and my Sekonic hand-held meter,
and I found that the OM4T was suspiciously low. Furthermore
I got inconsistent results using different lenses. Since one of the
lenses was obtained from Tom, I had a little off-list discussion
with Tom Scales, and in the end he suggested I consult the list.
So today I controlled my variables very carefully, and it seems
that zoom lenses with variable aperture (I have a Zuiko 35-105
f3.5-4.5 and a Carsen 28-70 f3.5-4.5) cause a meter variation
as they are zoomed. Not really surprising, but what does
surprise me is that the variation is much bigger when the
lenses are mounted on the OM4T, compared to the OM2n.
On the OM4T, I observed a very close to 1 stop variation as
the lens was zoomed from 35mm to 105mm. On the OM2n I
observed no more than a 1/2 stop variation. This metering
difference also was apparent in the viewfinders, with a
quite noticeable darkening (consistent with 1 stop) occurring
on the OM4T, and a very slight darkening ocurring on the OM2n.
The conditions were, camera mounted on a tripod, pointed
at a featureless interior wall, artificially lit. The lenses were
set to infinity focus, at f8 (but not stopped down with preview).
The batteries were new silver oxide. (In this process I discovered
that the OM4T had the WRONG batteries - witness yesterdays'
postings. It turns out that most of the variations and inconsistencies
I had originally observed, were due to the LiMn cell which was
gently dying in the OM4T.)
So, can anyone explain this behaviour? Does it happen on other
OM4T's vs other bodies?
- Parzival
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