I'd like to discuss long lens technique. It is my nature to analyze and question why.

This web site describes what I believe is the prevailing "long lens technique" method:

Moose Peterson: http://www.moosepeterson.com/techtips/longlens.html

The basic idea is that putting your hand on the lens above the tripod stops vibration induced by anything in the system, including the mirror slap, or wind, or you own hands.

The physics of this escapes me.

First a longitudinal wave traveling the length of the lens will travel near the speed of sound of the material. The speed of sound in aluminum is over 4800 meters/second and in glass over 3900 meters/second. The differential of glass and aluminum will quickly damp waves that would travel the length of the lens in 1/8000 second or so.

Probably the largest vibration factor is rocking about the tripod attachment point. The natural frequency of such a vibration (call it a transverse vibration) will be at a much lower frequency than longitudinal vibrations. This vibration is a tortional pendulum (e.g. http://farside.ph.utexas.edu/teachin...s/node139.html ). This vibration is also analogous to a seesaw (not sure if everyone around the world knows. here is a wikipedia page: http://en.wikipedia.org/wiki/Seesaw ). Imagine kids playing on a seesaw and you want to stop their up-down movement. If you place your hand on the seesaw at the pivot point you will not likely stop the movement, and may not even be able to slow it down. To slow the seesaw down, you have the greatest effect if you grab and hold onto the end, either end. Same with telephoto lenses.

So, it seems to me the best long lens technique is to grab the end of the telephoto system. Since you operate the camera at the camera end and not the lens hood end, grabbing on to the camera with both hands and placing your cheek up against the camera is the best way to dampen vibrations. Firmly holding the camera like this has two effects: 1) gives you the greatest leverage against movement by wind, and 2) greatest leverage from damping vibrations from the camera and mirror slap. Your hands and cheek on the camera also provide a damping mass against mirror slap.

Does the two-hands on camera method work? It is the only method I use and I have produced tens of thousands of sharp images over the last decade with my 500 f/4 with multiple bodies, TCs and stacked TCs. I have tried the hand on the pivot point and personally do not think it is as effective. I would be interested to hear if others try this and what they think. Or am I missing something regarding the effectiveness of hand on the lens pivot point method?

Roger