Archived posting to the Leica Users Group, 2007/04/01

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Subject: [Leica] Re: Camera exposure precision
From: lrzeitlin at optonline.net (Lawrence Zeitlin)
Date: Sun Apr 1 13:45:58 2007
References: <200704011759.l31HwJWG038454@server1.waverley.reid.org>

On Apr 1, 2007, at 1:59 PM, lug-request@leica-users.org wrote:

> To stray slightly off-topic - this reminds me about last year when  
> I sent my
> M7 to Sherry Krauter to repair a busted rewind knob. While it was  
> there she
> determined that the shutter speeds were off by quite a bit. I had  
> no clue.
>
> KISS - Keep I Simply Stupid!

The legendary photo repairman, Marty Forscher, used to say that  
exposure precision in film cameras was wishful thinking. With  
mechanical cameras shutter speeds could off by more 25%. Light  
transmission in lenses of the same aperture could differ by 15 to  
20%. Exposure variation across the frame due to vignetting could be  
as much as two stops from the center to the edge. With good luck,  
these errors could cancel out. With bad luck they could add up to  
produce unanticipated disastrous results.

Fortunately this was a real problem only with color slides. Most  
negative films had enough exposure latitude to hide exposure  
inaccuracies.

Larry Z