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Re: [OM] mechanical and electrical shutter

Subject: Re: [OM] mechanical and electrical shutter
From: Mark Marr-Lyon <o9938156@xxxxxxxxxxxx>
Date: Wed, 22 Mar 2000 10:27:48 -0800
C.H.Ling wrote:

>Yes, 11ms is a time, the time for the shutter curtain to travel from
>one edge to the other. I remember it was 11-12ms for the OM-1, but
>there could be other interpretation, such as the complete cycle or the
>time to cover only the 36mm frame.

In the om-1 manual, it says "Use the shutter tester 7F7L1 and/or 7F7L3.
The speed should be 11.7-12.1ms at 1/1000 sec.", but it also has the 
diagram showing 13.5ms from one edge to the other.  I have no idea 
what the 7F7L1 or 7F7L3 shutter testers are, but I was wondering if
there is some standard distance that these testers measure the travel
times over.  It makes sense that the time specified from the tester is
smaller than the time it takes to travel the whole frame, since it would
be easier to make a tester that measured the time over some distance
smaller than the frame.

>I expected the shutter tester will only measure one point, one point
>at a time or a few point across the frame, it will not take average of
>the whole frame. It is very important to check the equivalent shutter
>speed at different area across the shutter, at least you have to check
>the left edge, center and right edge for a horizontal travel shutter. 

The exposure time can be measured by only using one sensor, which I've
already done.  There is a definite deviation in exposure time between
the left and right sides of the shutter, which is why I want to measure
the curtain speeds.  I can infer that the closing curtain is moving
faster than the opening curtain, since the exposure time is smaller
on the left (from the back) side of the shutter, but I can't tell what
the actual errors are in each curtain.  Two sensors (at least) are 
necessary to do this, and I was trying to figure out how far apart to
mount them to get the times specified in the repair manual.

I realize that I'm probably splitting hairs about this, but I'm also
having fun doing it :)

Mark Marr-Lyon

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