Archived posting to the Leica Users Group, 2001/12/12

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Subject: [none]
From: Herbert & Lee Kanner <kanner@acm.org>
Date: Wed, 12 Dec 2001 10:53:45 -0800

"The TTL uses a electronic flash sync and will not fire the flash if the
shutter speed dial is set above 1/50.

John Collier"

I think the questioner deserves an explanation of why this is.  The 
focal plane shutter sets up a slit of varying widths.  For speeds of 
1/50 and below, the width of the slit is the length of the 35 mm 
frame.  For speeds below 1/50, the curtain pauses with the open slit 
in position for the required length of time.  For speeds of 1/50 and 
above, the slit travels across the film at a fixed speed. The way 
higher shutter speeds are obtained is by making the slit narrower. 
So, when set, for example, to 1/250, each spot on the film is exposed 
for 1/250 second, but the total time the slit spends travelling 
across the film is still 1/50 of a second.  Hence, if the flash were 
permitted to fire, only a narrow band of your negative would get 
exposed.

Herb

- -- 
Herbert Kanner
kanner@acm.org
650-326-8204
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