Hi, all. A new bunch of (late) replys...
>From: Moose <olymoose@xxxxxxxxxxxxxxx>
>
>Which is why the OMs in Auto mode (not spot) show you the
>exposure they estimate they will use, then make a final calculation with
>mirror up and lens stopped down before actually making the exposure.
I don't think so. I know of several cameras that do such thing (Min*lta
XD11, Nik*n FG/FA) but AFAIK that's not the case with the OMs (not sure
about the 40/PC).
Meter readout is, of course, an estimation of actual exposure time, based
on wide-open metering and relying on the position of aperture ring -- the
'classic' metering as most cameras do. Spot metering has no OTF, thus works
in a similar way.
But OTF metering doesn't take any previous reading into consideration: just
starts integrating actual light level upon release of the first curtain
and, when the proper illumination is reached, metering stops and the second
curtain is released.
>This is done even in OTF mode to determine if the exposure is faster
>than 1/60 and thus cannot be monitered and adjusted during exposure.
I think I understand what you're saying... OTF *always* monitors light
level during exposure time, but its job finishes upon release of the second
curtain. That will stop the exposure 'immediately'... at the left hand of
the frame (where the 2nd curtain appears), but the curtain will take about
1/60 sec. to reach the right hand side of the picture, completely finishing
the exposure.
If there are light level changes during a *long* exposure (low light), this
1/60 delay is negligible, and the whole frame would be evenly exposed. But
if expected exposure is over 1/60, both curtains will run with a fixel
width slit, regardless of (very fast) changes of light level. The left hand
side of the picture is likely to be correctly exposed, though. But there's
no 'toggle' between two 'modes' (over 1/60 vs. below 1/60), it's just a
limitation of the system.
>>The OM lenses really work best on the OM bodies
>>
>Of course. However, they also work rather well on DSLRs.
I agree.
>OK, so I did a test on the 300D with a 50/1.4
><http://www.moosemystic.net/Gallery/300Dexp.jpg>.
My experience with the 300D and adapted lenses (no matter the mount)
matches Moose's tests: above 1-stop overexposure @ f/1.4, about half-stop
over @ f/2, correct exposure between f/2.8 and f/11, and slight *under*
exposure @ f/16 (I seldom stop down that much -- especially on the 300D)
However, the overexposure at large apertures isn't anything new... I've
seen all kinds of mechanical compensation systems in every mount I know
(OM, Yash*ca/Cont*x, Pent*x K,Can*n FD, Nik*n F...) for lenses faster than
f/2.8.
>While Auto uses evaluative exposure on the 300D, Manual Mode uses center
>weighted, with much more stable results.
As already posted, evaluative metering could be fooled by stopped-down
metering. I usually prefer 'partial' metering, either with the kit lens or
adapted lenses.
>Light level was moderate, I'll try another lens and/or light level.
Most of my testing & shooting are done in low light levels. However, I've
made a quick test in much brighter light and got comparable results.
Enjoy,
...
Carlos J. Santisteban
<cjss@xxxxxxxxxxxxx>
<http://cjss.galeon.com>
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