Archived posting to the Leica Users Group, 2001/12/30

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Subject: [Leica] Mirror flapping and tripod dissertation
From: Jim Brick <jim@brick.org>
Date: Sun, 30 Dec 2001 13:33:03 -0800
References: <3C2F4176.A627D222@camera-craftsman.com>

At 11:21 AM 12/30/2001 -0800, Henry Ting wrote:

>  but quite frankly mirror flapping is
>only detrimental to closeup macro.


Actually, the SLR mirror effects ALL photographs taken with a shutter speed 
between a 1/30 and 1/4 second. Not just close-ups. It kills the recording 
of fine detail. The reason is that the mirror hits the top and the 
diaphragm closes down just before the shutter opens. The mirror vibration 
is at its peak just when the shutter is open and the vibration lasts for 
roughly 1/30th second. Long enough to be fully captured with a shutter 
speed between 1/30 and 1/4 second. Shorter shutter speeds (1/60 and higher) 
are over before the vibration wave hits its peak. With longer exposures 
(1/2 second and longer,) the vibration is a very small percentage of the 
total exposure time and therefore is not recorded.

Carbon fiber and wooden tripods will help dampen camera vibrations by 
absorption while steel and other all metal tripods tend to echo the 
vibration, and in some cases, amplify the vibrations putting the vulnerable 
shutter speeds all the way down to 1 second. The vibration wave sent 
through the metal tripod echoes back into the camera as a second vibration 
thus extending the vibration period.

Throw a rock into the center of a small pond. The waves radiate out from 
the rock hit, toward the bank then echo back, from the bank, to the center, 
where the rock hit. It is the same in a metal tripod. The camera vibrations 
radiate out (down the legs) and echo back to the camera. This does not 
happen in either a wooden tripod or a carbon fiber tripod.

If you have an SLR without MLU and want to photograph in the 1/30 to 1 
second range, buy wood.

Jim

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