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Re: [OM] Low light photography

Subject: Re: [OM] Low light photography
From: "John Hermanson" <omtech@xxxxxxxxx>
Date: Wed, 27 Oct 1999 11:02:12 -0400
The 2N has a dual duty limiter, one is the LED which is plugged into the
side of one of tthe silicon blue photodiodes in the mirror box floor.  When
3.5 minutes is reached (this is timed out by the small circuit board in the
bottom of the camera) the LED blinks, closing the shutter.  Also, if the
mirror  is left locked up (after shutter lock and you forget to reset the
shutter with either battery check or going to B)  the P circuit (bottom of
camera) turns battery drain off after 3.5 minutes.
The 2N LED flashes at the same  intensity regardless of ASA setting whereas
the 2s LED brightness is based on ASA.  Low ASA = low LED  light, high ASA =
bright.  So, low asa low light photography gives you a much longer auto
shutter speed.  My tests show an exposure maximum of about 20 minutes at ASA
12 and about 15 seconds at ASA 1600.  Tape eyepiece with black tape if you
are going to try testing your OM-2.

John
________________________________
Camtech, Olympus Service since 1977.
21 South La. Huntington, NY 11743
516-424-2121,  http://www.zuiko.com
________________________________
----- Original Message -----
From: <HI100@xxxxxxx>
To: <olympus@xxxxxxxxxxxxxxx>
Sent: Tuesday, October 26, 1999 10:42 PM
Subject: Re: [OM] Low light photography


> Wayne.Harridge@xxxxxxxxxx writes:
>
> <<
>  Can you explain something about the "LED limiter" >>
>
> Wayne,
>             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.
>
> Regards,
> Tim Hughes
> Hi100@xxxxxxx
>
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