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

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Subject: Re: [Leica] Reciprocal shutter speed rule
From: Henning Wulff <henningw@archiphoto.com>
Date: Sun, 6 Apr 2003 11:34:22 -0800
References: <45A8A863-685C-11D7-A82F-003065D6E648@umich.edu>

At 2:19 PM -0400 4/6/03, Dante Stella wrote:
>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.

Higher shutter speeds reduce the effects of camera shake until other 
factors such as atmospheric haze, lens aberrations, film 
grain/resolution limit mask it. Sync speed has nothing to do with it, 
nor does FP or leaf shutters. Leaf shutters have some other issues, 
such as induced vignetting, which affects apparent DOF at high speeds.

Yes, small distortions occur; these were noticed and demonstrated 
easily with early FP shutters on large cameras but are less 
noticeable the higher the sync speed is. FP shutters travel at the 
same speed even at 'slow speeds', not just at speeds over the sync 
speed.

In general, with a 6x9 camera and a 100mm lens, 1/60s will give you 
the same results as 1/60s with a 35mm full frame camera with a 50mm 
lens, as long as the print size is the same. It's a matter of 
magnification.

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    *            Henning J. Wulff
   /|\      Wulff Photography & Design
  /###\   mailto:henningw@archiphoto.com
  |[ ]|     http://www.archiphoto.com
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Replies: Reply from Mark Rabiner <mark@rabinergroup.com> (Re: [Leica] Reciprocal shutter speed rule)
In reply to: Message from Dante Stella <dante@umich.edu> ([Leica] Reciprocal shutter speed rule)