About the 308's (3413 Bogen #) problem - I discovered what causes it
now, and even found out a remedy which hopefully will work well,
otherwise I will just abandon ballheads and get #329 3-way, much
bigger, heavier and bulkier head (also costlier, somewhat). The
shifting of composition with the 308 was against the whole idea of
ballhead to me - to be able to quickly compose and quickly make camera
rigid, then recompose, again,...
The problem:
when tightening the ballhead, it always rotated more or
less around the vertical axis, to the right. So (especially with long
lenses) the composition shifted to the right when tightened.
A quick remedy (will it work always? Don't know, must try more):
Best would be having same lever as on #352 - it is centered so the
action of tightening doesn't impart that much rotation to the
casing. But if you rest your thumb on the tripod, and hold it
steady, and now tighten with the remaining fingers, it sort of
balances out the rotation. At least it worked with a 2.8/180 lens now
when I tried it. If the center column is extended hold your thumb on
the column platform.
more technical:
The ball in 308 (and propably other similar heads) is tightened by
forcing it against upper "bowl", which is formed by the big black
casing, forcing it by the lower bowl, which forces it upwards against
the black casing, limiting its movement until rigid. In fact, the
lower bowl rides greased on the main stud, which is screwed tightly
onto the tripod screw. This stud is completely stationary. On thick
layer of grease rides the lower bowl. The stud has conical sides, and
the tightening screw presses more and more (as it is tightened) onto
those conical sides with its conical tip. So in fact the lower bowl
remains stationery (although floating on grease to allow for smooth,
fluid movement), while the upper "bowl" (the black casing, in which
the tightening screw is) presses
the ball down. It's all relative :)
The conical tip should be independent of the screw it's placed on top
of, but unfortunately not enough in practice. So the motion of
tightening the lever is imparted via the stud's conical sides on the
black casing, which rotates to right a little, which in turn imparts
the rotation on the ball itself. Remember, this happens in phase where
the ball is almost tight, so the casing (upper bowl) does have enough
friction against the ball to impart the rotating motion to it.
More testing is needed, but perhaps I will not return the head after
all. I wanted ballhead so I could set-up quickly, the 055 NAT is also
very quick to set up, a 329 head is much slower for me.
Please excuse any blatant technical or language errors - it's pretty
hard to express technical things if English is not your native
language and you don't have degree in technical science :) That's also
the reason for so long post. Sorry.
Frantisek
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