A final word on the sack of shot thing. A couple of writers seem
to have misunderstood its purpose, apparently believing it's just
to add weight to the photographic ensemble. That is not the
purpose. Weight can easily be added to the tripod any number of
simple ways, such as hanging the camera bag on it, or you might
carry one of those old mesh potato sacks and enlist the aid of a
local rock or two.
Because of the physical characteristics of the loose, heavy lead
shot in the bag, hopefully making maximum contact with the
equipment, it absorbs and dampens the vibrations within the
camera/lens combination caused by the mirror flopping up and the
diaphragm slamming semi-shut. Though the added weight may be of
some benefit, it is not the object of the exercise. A brick or a
book or a small, furry animal atop the gear would not serve the
same purpose, and a Mack truck hanging from a tripod made of
reinforced concrete will have no effect on vibrations inside the
camera.
Any hi-fi nuts out there may be familiar with this notion. Being
also a vinylholic, I have to admit that's where I got the idea.
Some of the high-end equipment stands for turntables have hollow
legs which you fill with lead shot to dampen vibration.
Walt Wayman