Archived posting to the Leica Users Group, 2003/04/06

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Subject: Re: [Leica] Reciprocal shutter speed rule
From: "Roland Smith" <roland@dnai.com>
Date: Sun, 6 Apr 2003 20:42:22 -0700
References: <45A8A863-685C-11D7-A82F-003065D6E648@umich.edu>

You bring up a consideration that I have been curious about for a long time.
The focal plane slit may have a speed increase effect that can offset
movement based on the interval of light passage in the opening of the
curtain.  Does this totally compensate for the constant speed of the
curtain?

I remember using a 4X5 speed graphic focal plane shutter an 1/1000 and
getting distortion of the wheels of a speeding racing car.  That would seem
to give a clue that camera movement would be recorded.

Roland Smith
Oakland, California
- ----- Original Message -----
From: "Dante Stella" <dante@umich.edu>
To: <leica-users@mejac.palo-alto.ca.us>
Sent: Sunday, April 06, 2003 11:19 AM
Subject: [Leica] Reciprocal shutter speed rule


> I know it's shorthand (and I usually set the highest speed I can get),
> but...
>
> Does this rule even work about the synch speed of the camera when you
> use an FP shutter?
>
> When you use an FP shutter with speeds higher than the synch speed, the
> shutter is always traveling at the synch speed (the slit narrows but
> the curtains go at the same rate).
>
> So if you use, say a 500mm lens, and it is bouncing around as you hold
> it, isn't the shutter recording little distortions a slice at a time,
> even if it is at 1/500?  On an SLR with a 1/125 synch and lenses under
> 135mm, I have never noticed any additional benefit to using speeds
> higher than 1/125.
>
> Or is it that this rule only applies at high speeds to leaf shutters.
>
> Since most leaf shutters are on MF cameras, then does the magnification
> of the lens come into play?
>
> Example: 40mm lens on an SLR - pick 1/60 sec.
> 100mm lens on a 6x9 rangefinder - should it be 1/60 (based on
> magnification) or 1/125 (based on lens length)?!  I generally pick
> 1/125 if I can.
>
> ____________
> Dante Stella
> http://www.dantestella.com
>
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Replies: Reply from "Don Dory" <dorysrus@mindspring.com> (Re: [Leica] Reciprocal shutter speed rule)
In reply to: Message from Dante Stella <dante@umich.edu> ([Leica] Reciprocal shutter speed rule)