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Re: [OM] OM4Ti - Memory Function

Subject: Re: [OM] OM4Ti - Memory Function
From: Jan Steinman <Jan@xxxxxxxxxxxxxx>
Date: Tue, 3 Aug 1999 10:03:16 -0700
From: Chuck Norcutt <norcutt@xxxxxxx>

We need a timing gizmo with TTL cable inputs and outputs that gets
activated by the camera's "turn on the flash" signal.  It passes this
signal on to the flash and then sits there counting microseconds while
it waits for the "turn off the flash" signal.  When the command comes to
turn off the flash the timing gizmo forwards the command to the flash
and also stops its microsecond counter.

Sounds pretty simple. No digital needed. An integrator, comparator, and some switches. Two ICs max: 74TL041 and 4066. The most expensive bit would be the TTL connectors, coming as they must from Olympus instead of DigiKey or such.

With an analog design, there's no timer, just a voltage on a capacitor.

... Actually, it won't completely ignore the "turn
off the flash" signal since it may be desirable to use that signal to
feed back an exposure OK signal to the camera...

But you've just defined "OK" when you locked the exposure! While it might be interesting to know if your locked exposure is over or under the TTL-calculated exposure, I think it would be bad ergonomics to "re-use" the OK indicator for that purpose. (Look how much trouble the re-use of the memory lever on the OM-4(T(i)) has caused... :-)

... Maybe we should just use a toggle switch
with labels.

With the analog design, each exposure would be memorized, flipping a switch would switch the timing capacitor from the integrator to the comparator. In effect, it would say, "continue using the last memorized exposure."

... OK, who can turn the logic into hardware?

Lots of people -- the real question is, "who can fund this effort?" It's probably a week of evenings plus a weekend for a prototype. I'll put it on my "future projects" list, which means I might get to it shortly after my Databack 4 runs out of dates... :-)


: Jan Steinman <mailto:jans@xxxxxxxxxxx>
: 19280 Rydman Court, West Linn, OR 97068-1331 USA
: +1.503.635.3229

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