Re: [Leica] Checking a tripod for resonance

[George Huczek <ghuczek@sk.sympatico.ca>]

At 04:27 PM 04/08/98 -0700, Henning wrote:
>The more accurate way to test for vibrations is to use a small mirror stuck
>onto camera, lens or tripod head, point a small hand laser at it and have
>the light bounce onto a flat surface. The further the travel distance from
>mirror to wall, the more sensitive the test will be. Fire the shutter, and
>watch the light dance. The reason this works better is twofold; if the
>mirror to wall distance is long enough, the test will show vibrations that
>you would never see with the water glass. Also, a small mirror has much
>less inertia than a glass of water, and will not likely have its own
>resonant frequency that is close to the camera/lens/tripod system.

I'll try this in the next few weeks, when I get some time.  It is extremely
sensitive.  An x degree movement of the mirror causes a 2x amplification of
the reflected beam.  With a long "throw" to the wall, extremely small
deflections can be measured, and unlike the water, there is less dampening.
 In the past I have used a laser like this to demonstrate the amount of
bending that happens in a table when a book is placed on it!  The laser I
use is currently off being repaired.  It had a standard 1/4" tripod socket
which will enable me to set it up on a second tripod and do this test very
accurately.  
   One thing to be careful about, depending on the type of laser being
used, ... make sure you don't look directly into the beam from the laser.
It could cause serious eye damage.


- -GH