Re: [OM] OM4Ti - Memory Function

Subject: Re: [OM] OM4Ti - Memory Function
From: Chuck Norcutt <norcutt@xxxxxxx>
Date: Mon, 02 Aug 1999 21:52:19 -0400
Well, it looks to me like a (maybe not so challenging) challenge for Tim
Hughes.  When I first read Han's reply to Paul about memory and TTL
flash I thought that the memory could also be in the flash or, better
yet, the memory/timing circuit could be independent and located between
the camera and the flash.

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.

Pressing a button on the gizmo will now lock the timer value.  Now, when
the camera is fired again, the gizmo will forward the "turn on the
flash" signal as before but will ignore the "turn off the flash" signal
in favor of it's own flash quenching command which will be controlled by
the stored timer value.  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.  If the voltage is OK
maybe that same signal can just be routed right back to the camera.

Pressing the button on the Gizmo one more time will clear the memory and
set it up to record another timer value.  Oooops!  Now we need an LED to
indicate which state it's in.  Maybe we should just use a toggle switch
with labels.

Now you can use your 18 0ray card for TTL flash!!!  Remember, you saw
it "exposed" here first!  OK, who can turn the logic into hardware? 
Tim, are you there?

Chuck Norcutt
Woburn, Massachusetts

Hans van Veluwen responding to Paul Schings:

Paul Schings wrote:

: The thing that intrigues me is that Hans is saying here that MEMO
works with
: TTL flash as well. I wasn't aware of that, and don't believe I ever
read it
: in the OM-4 manual

Oooooops, my mistake. It was only wishfull thinking. Memo is disabled
when a T
flash is connected and activated, and when the memo function is already
and you connect and activate a T flash, the memo function is cancelled.
Any spot
metered value is cancelled as well. Oh well, at least I've found yet
method to disable the memo function. Can be handy when the spot reset
button is
scraped off by using off-brand lenses ;) And this flash memo function I
made up
is maybe something for the OM-6 wish list... because I think technically
would be no problem?

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