Definitions
A Steadicam is in static balance when, at rest, it hangs with the central post vertical, regardless of the position of the gimbal on the central post.
An exception: If the sled is perfectly balanced top to bottom, it won’t hang vertically any more than it will hang at any other angle.
A Steadicam is in dynamic equilibrium if, when rotated about the central post, it pans consistently on that axis.
A Steadicam is in dynamic balance when it is in dynamic equilibrium and also in static balance. Both conditions must be met for dynamic balance.
Dynamic balance does not describe how fast or slow a Steadicam will pan when a force is applied. That is a separate – but related and important – subject of inertia.
A Steadicam can often be in static balance – i.e., it will hang perfectly upright – and not be in dynamic equilibrium, and therefore it will not be in dynamic balance.
In this condition, the rig will behave very oddly when it is panned. Prior to 1988, this is how Steadicams were routinely balanced (and designed!) because, in part, the Steadicam wasn’t considered a quickly rotating object. Today, opera- tors routinely do whip pans with rotational speeds in the order of 100 to 150 rpm’s, and dynamic balance is critical for this type of work.
A minor note: It is possible for a Steadicam to be in dynamic equilibrium and not be in static balance. While this condition is possible to achieve on planet earth, it is useful only in outer space when the Steadicam is weightless.
Why is dynamic balance important?
As an operator, one wants to be able to frame shots with precision. Properly balancing the Steadicam increases the precision of one’s operating.
If a Steadicam is out of dynamic balance, the operator constantly must make adjust- ments to keep the Steadicam level as it is panned. These adjustments reduce the precision of operating and can affect the quality or feel of the shot. The more the Steadicam is out of dynamic balance, the greater the corrective adjustments.
A Steadicam in dynamic balance will pan perfectly on its own, without constant adjust- ments by the operator. More precise pans and framing are the result.
Put another way, a Steadicam in dynamic balance will take full advantage of the excellent bearings and careful construction of the gimbal.
Dynamic balance fundamentals
Every component on the sled has a mass (or weight) and a position relative to all the other components. The major and most massive components are the battery, the monitor, and the camera.
Other components include the electronics, the junction box, the Steadicam’s structural elements, and any accessories such as a small VCR, a receiver for follow focus control, or a video transmitter.
Each component has an effect on both static balance and dynamic equilibrium.
Each component also has an effect on the inertial quality, or “feel,” of the Steadicam.
These effects can be represented mathematically, and a mathematical formula can be used to describe and/or find dynamic balance.
We can also use our understanding of the math to set up a rig and to test for dynamic balance empirically, without solving any equations.
Depending on the Steadicam model, the operator may have very few or a lot of choices in positioning the major components.
The operator first positions the major components in the best possible configuration for the shot, and then the operator balances the sled both statically and dynamically.