Tim wrote:
> The OM2/n limits long exposures so as not to
> waste battery life
> too much by feeding a small amount of light from an LED into the OTF
> photo-cell. This very low light level ensures that in total
> darkeness the
> shutter eventually closes after the low light is integrated.
> In the 2 the LED
> is on from near the begining of the exposure. In the 2n the
> LED only comes on
> after around 2 min and is brighter so giving a more
> controlled cut off time
> after 2 minutes. On the 2 this light is integrated along with
> light from the
> scene so at very low light levels (corresponding to minutes
> of exposure time)
> this causes an over erestimate of actual scene brightness and
> hence an under
> exposure.
>
Thanks Tim, it's an interesting way of handling that situation, I would
guess that it is not the first idea someone would come up with to save
battery life. Why wouldn't you just use a timer to close the shutter
directly after 2 min, or feed a small voltage directly into the integrator,
or put a high value resistor across the light cell ? I wonder if this was
an "add on" built in after the major part of the electronic design was
complete. I wonder if there are any really early 2s without this LED.
Wayne Harridge
Ivanhoe, Victoria, Australia
http://www.geocities.com/Paris/Louvre/6152/
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|