In program mode:
As mirror starts to move, circuit turns on
cell in mirror box reads light off first curtain to determine BV
(brightness value)
If, for example, light is BV 12 (asa 100) camera will fire shutter speed
around 1/200th, governor will set f stop between 4 and 5.6 (below BV7,
cameras shifts to larger f stop to boost shutter speed).
governor stops aperture arm at this preprogrammed spot.
As mirror nears the top, shutter fires
If light changes between when mirror starts to move and shutter starts
to fire, ttl takes over and varies the shutter speed but retains same f
stop.
Something like that.
___________________________________
John Hermanson | CPS, Inc.
21 South Ln., Huntington NY 11743
631-424-2121 | www.zuiko.com
Olympus OM Service since 1977
Gallery: www.zuiko.com/album/index.html
Ken Norton wrote:
> We've discussed this before, but I'm needing a refresher.
>
> What exactly is the shutter firing sequence for the OM-2S and is it
> different between Program Mode, Aperture Priority Mode and Manual Mode?
>
> Here is what I THINK happens in Program Mode--please correct.
>
> 1. Shutter-release is pressed.
> 2. Aperture actuator arm in camera closes down lens to smallest F-Stop
> allowed by len's aperture ring
> 3. Mirrors swing up
> 4. Exposure reading begins
> 5. If in Program Mode, the aperture actuator arm adjusts to new F-Stop.
> 6. Curtain Opens
> 7. Film Exposed
> 8. When sufficient light has hit film, Curtain Closes
> 9. Mirrors return to down position.
>
> Here is what I THINK happens in Aperture Priority Mode--please correct.
>
> 1. Shutter-release is pressed.
> 2. Aperture actuator arm in camera closes down lens to the F-stop set on the
> lens.
> 3. Mirrors swing up
> 4. Exposure reading begins
> 5. Curtain Opens
> 6. Film Exposed
> 7. When sufficient light has hit film, Curtain Closes
> 8. Mirrors return to down position.
>
> Here is what I THINK happens in Manual Exposure Mode--please correct.
>
> 1. Shutter-release is pressed.
> 2. Aperture actuator arm in camera closes down lens to the F-stop set on the
> lens.
> 3. Mirrors swing up
> 5. Curtain Opens
> 6. Film Exposed
> 7. Curtain Closes
> 8. Mirrors return to down position.
>
> It is my screwed up understanding that the main difference between the OM-2S
> and the other OM bodies is that the Aperture actuator arm is activated
> BEFORE the mirror goes up, whereas on the others it goes up either at the
> same time or just after the mirror goes up. The sequence of events with the
> OM-2S is definitely longer than that of the OM-3Ti and OM-4Ti and induces a
> substantial shutter-lag as a result. I'm just trying to grasp what these
> differences in sequences really are.
>
> AG
--
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