[Leica] Burning a hole in the shutter

[firkin at ncable.net.au (Alastair Firkin)]

Sadly it does not take that long: there died a wonderful untouched M3 
Shutter, and all because some bunny told me to sun my lenses to keep 
the fungus off ;-)

On Thursday, May 20, 2004, at 03:17 Australia/Melbourne, Peter Klein 
wrote:

> On another list, the subject of cloth vs. metal shutters has come up.  
> The danger of the sun burning a hole in the shutter curtain was cited 
> as an advantage of the metal shutter.
>
> In over 30 years of using Leicas, I have never burned a hole in my 
> shutter (knock on wood, ptu-ptu-ptu!) .  I wonder how long it actually 
> takes to happen.  Nowadays I often set my lens to close focus when I'm 
> facing the sun on sunny days, just in case.  But I never did this 
> before, and I never had a problem.
>
> I suspect normal body movement usually moves the sun's image around 
> enough so that the shutter doesn't "catch."  On bright days, lenses 
> are usually stopped down, so less energy reaches the curtain.  I 
> suspect that people have to leave the camera lying still in the sun 
> for an appreciable length of time for the shutter to "catch." And 
> probably the lens has to be fairly wide open and focused on or near 
> infinity.
>
> I'm curious how much of a danger this really is.  Has anyone heard of 
> someone actually testing this out--hopefully on an already bad 
> curtain!  :-)  Does anyone have any firsthand information about such a 
> test?  Or, would anyone who actually burned a hole in their shutter be 
> game enough to tell us how it happened?
>
> --Peter
>
> P.S.  I have seen one Leica with a burnt hole  in the shutter.  The 
> original shutter on one of my cameras had a little patch over such a 
> hole.  I don't know how it happened, because the previous owner said 
> he bought it that way.  I happily used the camera until one of the 
> curtain strings failed, at which point I had both curtains replaced.  
> It worked fine before, and it works fine now.
>
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Alastair