Hans van Veluwen wrote:
>
> > The OM-4 manual states an lowest EV of 0 for spot metering (with mirror)
> and
> > of EV -5 for OTF metering (exclusive mirror) at ASA100.
>
> :Yes, and experience bears this out. You must use OTF for the long
> :exposures. Spot mode won't go much past a few seconds.
>
> Well, not to my experience and certainly not according to the manuals. I
> have both the OM-4 manual (languages English / German / French / Spanish)
> and the OM-4Ti Black manual (English). Both agree that AE control by average
> light has a range of 1 min.-1/2000 sec, whilst the AE exposure control by
> *spot* measurement does the 'real thing': 4 min.-1/2000 sec. The manuals
> disagree however in their EV data:
>
> The OM-4 manual (page A-63) claims -5 EV ~ 19 EV for average light mode
> and -7 EV ~ 19 EV for spot mode.
> The OM-4Ti manual (page 130) claims +(sic!)5 EV ~ 19 EV for average light
> mode and 0 EV ~ 19 EV for spot mode.
Yes, I verified my 4T manual makes the latter claim. But it's gotta be
a mistake. I believe they switched 'em.
Experience: I've taken lots of moonlit landscape photographs. By
experimentation when I started doing this years ago, I found that with
100 Speed slide film and F/2.8 aperture that 3 min exposure would
usually give me just what I wanted (depending of course n the scene.) I
also found that my 4T on auto/OTF is practically dead-on as long as the
aperture isn't stopped down too far. My camera seems to max out in OTF
auto-exposure mode at ASA100 at close to 4 minutes, which is the claim
the manual makes for spot mode. However, I've tried some of these same
moonilit landscapes by spot reading a "middle tone" and I get vast
underexposure. I gave up on doing that.
Theory: To me, this makes sense. In spot mode, you take a direct,
immediate reading of a light level. If that light level is 'low' can a
millisecond spot reading possibly give an accurate reading? I mean this
relative to the OTF auto metering, which works by *integrating* the
light over the entire scene over time. This integration process allows
much finer and I believe lower light levels to be measured.
I'm interested in hearing your experience in this subject, Hans.
Thanks
George
>
> All data are given for 100 ASA with a 50/1.4 lens.
> I believe the first one. It corresponds with the time values.
> This is not the first time I've seen typos in the OM-4Ti manual. Check page
> 116 for the notorious Spacemen...
>
> Hans
>
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