Jostein wrote:
>>> AFAIK, no camera will give you TTL on B. After all, the whole
>>> concept of the B setting is to override every attempt from the
>>> camera to electronically control the shutter. [...]
>> Yeah, but TTL-flash mode tells the flash when to shut off,
>> not the shutter when to close. [...] So it's not obvious that
>> turning off TTL-flash mode when the camera is set to "B" would
>> _automatically_ be the right design decision [...]
>
> Seems counter-intuitive to me, but I see your logic.
>
> If having a setting on the camera with total manual control over every
> other aspect of the exposure, why put TTL functionality in it?!?
Well, to be fair, I'm not arguing that leaving TTL metering _on_
is "the obvious right design" either. But here's why it makes
sense to me:
I can turn off TTL-flash control _at_the_flash_, so
whether the camera still does TTL-flash on "B" or
not, either way I can resort to a fully manual mode
of operation.
If the camera doesn't do TTL-flash on "B", then one
possible combination of behaviours is unavailable,
one that most people will probably never need, but
that I can imagine a possible scenario for.
> Putting TTL sensoring into a B exposure would essentialy mean an
> off-the-film metering during exposure. Which is what the LX does on
> Auto (Never owned a Super Program...), so those settings would partly
> duplicate each other, wouldn't they?
Sort of, but not really. In normal TTL-auto mode, the LX decides
when to close the shutter based on the light that has come in during
the exposure. In TTL-flash mode, the Super Program decides when to
turn off the _flash_ based on the light that has come in during the
exposure, and I was under the (possibly mistaken?) impression that
the LX did the same thing in TTL-flash mode.
My understanding is that there's really no way something as slow
moving as a shutter can close quickly enough to compensate for
too much flash, which is why the LX would have to tell the flash
to quench like the Super Program does. (And if my understanding
is in fact correct, then the reason the trick of setting the camera
on auto and firing an off-camera flash multiple times works is that
you choose a flash power/distance combination such that each individual
firing of the flash is significantly less than enough for a correct
exposure ... if the last one is a little more than what was needed,
the exposure will still only be a fraction of a stop overexposed,
well within the lattitude of the film.)
> Performing metering would also use battery power, but (again) afaik, B
> settings don't use battery in cameras with mechanically controlled
> shutters (eg. LX).
Ah! Now that does matter, unless TTL-flash metering can be turned
off in response to detecting the lack of support for it from the
flash.
So the LX shutter was mechanically controlled _and_ electronically
controlled depending on the mode, then? Fascinating. That would
be important on "B", for sure. (IIRC, the Olympus OM-10, and from
looking it up on Boz's page, the Super Program, control the shutter
electronically at all speeds, making for significant battery drain
during really long bulb exposures.)
It's important to note, if it isn't already obvious, that I'm
not arguing about what the LX _does_ -- I don't have one and I
trust the folks who do. I'm arguing about what I might have done
slightly differently if I'd designed it. (Which puts the discussion
into the same degree of relevance as college students tossing
around philosophy questions over beers in the dorm late at night
after one semester of philosophy class, I guess.)
-- Glenn
