25
Looking good!
Spinning a bit wobbly.
We put the rig in dynamic balance by
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position. Then we discover the one-and-
only ideal position for the battery by the
trial and error method.
First, set up your sled at the proper
length for the shot and place the monitor
where you want it for proper viewing
and inertial control. Typically with the
Zephyr
™
stabilizer system, the monitor
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stop and two weights are attached to the
rod (see page 8). Two weights are also
attached to the battery rod.
Next, position the camera so that its c.g.
is about .5in (12mm) behind the center
post. The center post is just over an inch
in diameter, so you can use the back of
the post as a guide. Next, static balance
by sliding the battery in or out so that
the sled hangs perfectly vertical fore and
aft. Make sure the top-to-bottom balance
is set with a drop time of 2 to 3 seconds.
Trim side to side with the camera, using
the knobs on the stage. Fine-tune the
fore-aft balance with the camera. You
want the sled’s post perfectly vertical.
A spirit level will help you get the post
vertical.
Give the sled several careful test spins.
Very important: do not spin the rig very
fast – certainly not much faster than a
normal panning speed (3 – 6 rpm). Note
the results. Is it good or bad, i.e., does it
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is the sled out of dynamic balance?
If your sled is not in dynamic balance, do
not move the monitor!
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then rebalance statically with the camera.
There are only two directions to move the
battery: out or in. You have a 50% chance
of choosing the right direction, so stop
worrying about it and give one direction a
test. Just be sure to make a note of which
direction you move the battery.
Each time you lock the battery in a new
position, you must rebalance the sled
statically with the camera. Do not move
the monitor! Once you are in static
balance, spin the sled again. Is it better or
worse? Again, you have two choices for
moving the battery.
Re-rack, rebalance, and spin again (and
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should not take a lot of time.
When the battery is within about .25in
(6mm) of ideal, the sled will behave
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suggest you do not attempt to do this for
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Adding any accessory or extra Merlin
weights to the sled will affect both static
and dynamic balance. Changing the
length of the sled, and/or moving the
monitor in or out will change both static
and dynamic balance.
How much will dynamic balance change? It
depends on how much things have changed.
In practice, it’s a lot easier than it sounds
on the page, and luckily, there’s one
great gift in all this: it doesn’t matter for
dynamic balance what weight camera you
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etc. Really!
So if you make any changes with the
camera – or use a different camera –
there are no worries about getting back
in dynamic balance! You only need to
rebalance statically and you will be in
dynamic balance again. Honest.
Put the other way around: you can set up
your rig in various ways with a practice
camera at home, making it long or short,
monitor in or out, with an extra weight,
etc. Just note or mark the positions of the
monitor and batteries, and you will be
able to get into dynamic balance quickly
on set, regardless of the camera you
carry. Really. Honest. No fooling.
For the complete story, see the Dynamic
Balance Primer and play with the
Dynamic Balance Spreadsheet, available
online at www.steadicam.com.
Dynamic balance spin test with an Ultra
2™
