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Re: [OM] OM Metering for long exposures

Subject: Re: [OM] OM Metering for long exposures
From: "Shawn Wright" <swright@xxxxxxxxxxxxxx>
Date: Thu, 24 Sep 1998 14:33:59 -0800
On 24 Sep 98 at 22:15, Konrad Pizzuto wrote:

> Hi,
> 
> Can anyone help me out?  How does one calculate the time needed for a
> long exposure (more than 1sec) using an OM-10?
> 
How long? I've done 5-15 second exposures on auto with my OM-10 with no 
problems. (ISO 100 film).

If your manual control (and have the adapter) try taking a meter reading at ISO 
1600 and wide open, then adjusting for your intended film speed and aperture.

ie: if ISO 1600 and f/2 gives 1 sec, then ISO 100 and f5.6 would be:

Adjust for ISO:
1600
800
400
200
100
= 4 stops = double the exposure 4 times
= 16 seconds at ISO 100, f/2

Then adjust for aperture:
f/2
f/2.8
f/4
f/5.6
= 3 stops = double exposure 3 times
= 128 seconds!

I would add bracket at least 1 stop over the above time for reciprocity 
effects, ie:
shoot 1 at 128 seconds, then one at 192 sec (+1/2), and one at 256 sec (+1).

And if you're times are this long, make sure the batteries are fresh!! The 
OM-10 will use power to keep the shutter open on B.

Hope this helps.
========================
Shawn Wright
Computer Systems Manager
Shawnigan Lake School
250-743-6240
swright@xxxxxxxxx

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