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Re: [OM] OM-4T Multi-Spot Metering

Subject: Re: [OM] OM-4T Multi-Spot Metering
From: Dan Lau <dlau@xxxxxxxxxxxxxxxx>
Date: Wed, 13 May 1998 09:37:34 -0700 (PDT)
On Wed, 13 May 1998 08:31, gma <gma@xxxxxxxxxx> wrote:
>Here's the way it works on the 4, it's pretty slick:  When u first power up,
>the bar graph moves in real time, indicating the appropriate shutter speed in
>CENTER-WEIGHTED mode. Now, if you press the spot button, you'll store a (spot)
>reading at that spot (may not be the same as the center-weighted reading) and
>then the bar graph AND a little diamond will indicate the shutter speed.  Both
>these indicators are now fixed but another little diamond now appears which
>moves in real time indicating the SPOT reading for where you're pointing the
>central spot now. If you press the spot button again, that second diamond
>becomes fixed at that spot AND the bar graph moves to a point between the 2
>diamonds and equidistant from each.  This bar graph now indicates what shutter
>speed will be used for the subsequent exposure, ie the average of the 2 spots.
>In adddition, a third 'real-time' diamond has appeared and the process can be
>repeated up to eight readings.

>Hope this helps.

>george

>PS. Put another way: It's always in 'real-time' mode, center-weighted with the
>bar graph until you press the spot button, spot mode thereafter with the moving
>diamond.

Thanks, George, for the explaination.  I don't own an OM-3/4 yet, but it
is always in the back of my mind that someday when I can afford it, I'll
get one.

Based on the above, it seems the following happens:
- The camera is alwasys in center-weighted mode until the spot button is
  pushed.
- Pushing the spot button will put the camera into spot mode AND record
  a reading in memory (shown with a fixed diamond).
- The camera continues to do spot reading with whatever is in the center
  of the viewfinder, shown with a moving diamond.
- The (moving?) bar indicates the current suggested exposure.

This brings up another question: after one reading is made, does the
"continuous/instantaneous/real-time" reading enter into the exposure
equation when the shutter is pressed?  In other words, after one reading,
is the bar at the same spot as the fixed diamond and the bar does not
move until another spot reading is recorded (i.e., the spot button is
pressed again)?  The camera may be doing continuous spot readings in
real-time, but if the reading does not enter into the exposure equation,
then the continuous readings are useless (which is not good).  On the
other hand, if the continuous reading is part of the equation, then it
is always averaging between the remembered spot readings and whatever
is finally in the center of the frame when the shutter is pressed
(which is not good either).

Second question, does adjusting the high-light/shadow or exposure
compensation cause the bar to move or are there other indicators in
the viewfinder that these actions were taken?
        -Dan

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