I have made side to side comparison with my OM-4 (good one) and 4Ti (fault one).
With the same lens and same reflective media (same piece of film) I was lucky
that both got the same meter reading (I know meter reading not related to film).
But the 4Ti's auto exposure read a longer shutter speed - 2/3 stop or more at
1/60s and below. There is NO problem above 1/60s (by setting the memory on,
you can see the actual exposure reading in auto mode).
For the 2sp I had, I have tried to point to a darker area, stop down the
aperture one by one, count with an analogue watch, the exposure time just not
increase in the order of 1,2,4,8,16 but non linearly. I can't remember exactly
but could be 1,3,10,40.... While my OM-4 and 2n is exactly 1,2,4,8,16... My 4Ti
also increase non linearly but not as worse as my 2sp.
A slide test already confirmed my 4Ti is over exposed at below 1/60s, while the
manual exposure is very accurate. Anyone care about their camera's accuracy at
low light level can perform the test I mentioned above, it is very easy just a
stop watch can do.
P.S. not every 4Ti have the same problem, one of my friend's Champagne 4Ti is
good.
C.H.Ling
>
>I can't comment on the particular problems of this, or any other, camera,
>but there are a couple of other possible reasons for discrepancy between
>manual and auto that haven't yet been mentioned on this thread.
>
>1. OTF/OTC auto exposures are metered with the lens stopped down to the
>taking aperture, whereas manual and spot readings are taken wide-open. For
>the latter to meter correctly requires that:
>
> - The *difference* in brightness the selected aperture setting and
>wide-open is
> accurately signalled from the lens to the body, to allow for
>correction
> of the metered light reading by the electronics.
>
> - The stop-down of the lens prior to exposure precisely matches this
>signalled
> information.
>
>Since both the signalling and the stop-down are controlled mechanically,
>there is at least the possibility of slop or inaccuracy in the lens linkage,
>the body, or both (this would be less likely to affect exposures made with
>the aperture set to wide-open).
>
>OTF/OTC auto is not affected by such errors.
>
>
>2. OTF/OTC auto exposures are metered with the mirror up, whereas manual and
>spot readings are taken with the partially-silvered mrror in the down
>position. There is hence a possibility of light leakage from the eyepiece,
>although it would have to start out pretty bright to have any effect as it
>is attenuated first by the focussing screen, then by the mirror and finally
>by the shutter curtain.
>
>Since (IIRC) only one of the shutter curtains carries the metering pattern
>(the other is black) the meter display would vary according to whether the
>shutter was cocked or not, if such light leakage were occuring.
>
>
>I don't really know how likely it is for either of these possibilites to
>affect the meter reading, or to that degree, but it is interesting that in
>both cases it would be the OTF/OTC auto exposure that would be correct, and
>not the manual/spot value.
>
>-Brian
>
>< This message was delivered via the Olympus Mailing List >
>< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
>< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
>
>
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|