priit@xxxxxxxxx wrote:
> On Wed, 27 Jun 2007, Lukasz Grabun wrote:
>
>> Would someone enlighten me what is wrong with my thinking and why did
>> the camera metered the light the way it did?
>>
>
> I tend to somewhat disagree with what has been said before. Intuitively it
> seems to me that your thinking was correct and that the center weighted
> meter should have caused underexposure at +/- 0 with the way you framed
> #5. Of course this is assuming the ratio of sky and ground is the same in
> all the bracketed shots.
>
Lukasz said that these were all metered in Auto Mode because there is
something wrong with manual on his camera. As you know, these are two
completely separate metering systems. What may not be obvious is that
the Auto OTF-TTL metering is full frame average, not center weighted.
Manual and the in-viewfinder indications for Auto are center weighted,
but not the actual Auto exposure itself.
Early OM-2 bodies were vertically center weighted, but the curtain
pattern was changed and remained that way for the 2n.
http://brashear.phys.appstate.edu/lhawkins/photo/om2-curtains.shtml
Oly was very coy about this, as center-weighted metering was an initial
feature of the OM-2 and the viewfinder metering remained that way. The
OM-2n manual says:
"Automatic exposure control: Aperture-preferred automatic exposure
control electronic shutter type. TTL Direct (off the film) Light
Measuring System.:
"Manual exposure:, TTL type. Measuring system: Full aperture center
weighted metering."
I'm not sure it makes much difference with this rather symmetrically lit
subject, but center weighted metering is not in play here.
Looking at the image in PS, the mean luminosity of the whole image is
146 and that of an oval roughly proportioned by eye to the proportions
of the frame and covering maybe 20% of the whole image area has a mean
of 145. Cropping the image to the central portion also gives about the
same mean luminosity, so center weighting probably wouldn't be an isue
an issue here anyway.
Moose
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