Introduction to Intertial Camera
I have been retired for several years
and the cameras and systems mentioned here may not be the latest. However the
laws of physics have not changed much since. Understanding the theory of inertial
stabilization will help you use a ready-made device or to build your own. Before
building one consider whether an existing device will do your job well and that
doing bad work with a homemade rig might threaten your reputation. Consider
hiring a trained operator with his own device. Owning a device allows you to
practice on your own without shooting film. Some consumer/prosummer camcorder
stabilizers are over priced and some poorly engineered. Building one might be
wise if you are a mechanic and understand the principles, hopefully explained
here. If not, consider buying, borrowing or renting an industry accepted device.
AS WITH ANY TOOL, a lot of practice is crucial. Donít risk your reputation by
trying to learn on the job. (This applies to any new skill.) A non-body attached
camcorder size unit would be good practice for walking, framing and learning
some of the skills needed for the larger body supported units.
I am reluctantly creating some new
definitions and I suggest that you download and study the pictures in "Hand
Held Vertical TEE Rig for Camcorders", "Low POV Rig" and "Heavy Horizontal TEE
Rig". Also read "Industry Standard Examples".
INERTIA: the tendency of a mass at
rest to remain at rest or if moving to keep moving in the same direction unless
affected by some outside force. That is what it is all about.
We use inertia in many ways to keep
cameras stable or make them move smoothly. Cranes and stage dollies with lots
of inertia take force from grips to get them moving and to stop them smoothly.
(Some times you have to first overcome inertia to get the grips moving.) The
old long and heavy studio TV cameras could be panned and tilted smoothly without
fluid dampening because they had a lot of inertia.
CENTER OF GRAVITY (CG) is the point
about which the weight of an object or group of objects is balanced in space.
If a rigidly connected group of objects is supported at its CG, it will remain
stable or if moving will continue moving in that direction until affected by
an outside force, ideally guidance by an operator.
A barbell has much more inertia than
a single concentrated weight. This is the most important principle of inertial
camera stabilization. The best illustrations of pioneering designs of inertial
camera stabilization are Nelson Tyler's Helicopter Mount and Garrett Brown's
Steadicam. Inertia allows the camera system (camera and counterweights) to remain
stable or move smoothly in the same direction while isolated from the undesired
motions of their support; a helicopter, a vehicle or the operator's body.
Good designs are also "ergonomic":
the design of equipment to be operator friendly and integrated around the design
of the human body. (My definition.)
Many older hand held camera designs;
the Bell and Howell Eymo/Filmo, Arri 35 II models, and Bolexs were poor examples
of ergonomics and design for inertial stability. They also relied entirely on
the operatorís arm to support the camera's weight. Newer cameras, such as the
Arri BL and Betacam designs spread out camera's weight and put the center of
gravity and support point over the shoulder making the cameras more inertially
stable. Their eyepiece is also positioned more convenient to the operator's
An operator can learn to overcome
many of the faults in the ergonomics and balance of a camera, but good design
will make using a camera much easier. I am amazed at the smooth walking dolly
shots made by TV news Betacam operators.
A well-balanced and designed inertially
stabilized device should remain in any position or continue in a direction on
its own and change framing with a gentle touch from the operator. If a device
tends to go in some direction on its own, it is not properly balanced, the connection
system is not in the right place or the isolation system is not properly designed.
We have made inertial stabilized
rigs up to 20 feet long with tension cables like a sailboat mast for rigidity.
We built one for shooting horses from a pickup truck driving on very rough ground
for "Black Stallion". Bill Bennett built Terraflite for "Black Stallion II" that pans, tilts the camera and corrects the horizon. Every moving element is
balanced about its CG. Ray Tostado built a long one for shooting boat to boat.
(A very skilled driver piloted the camera boat.)
It pays to make a prototype as simple
as possible to see how well a rig works, improve its ergonomics and learn the
parameters. Make a mock camera the same weight and size of your camera to use
for prototypes and practice. Bricks can be hot glued or epoxied together. "Tee" nuts and plywood will make a base to attach as a real camera would. (See Map
Reading / The Map Table/ TEE Nuts) Place the mounting thread relative to where
they are on the real camera. Bricks can be cut with an abrasive saw or broken
to size if too heavy. 4x4 or 4x6 lumber will also make a mock camera. (See Shaki
Cam Practice Rig)
Pressure from the operator's eye
up to the eyepiece can introduce unwanted movement from the operator to the
camera and the regular eyepiece position is rarely convenient when the camera
is in a rig. Some kind of accessory finder is necessary. Light leaking through
the eyepiece of some film cameras is also an issue.\
For very wide-angle moving shots,
sometimes no viewfinder is necessary. You can concentrate more on footwork,
obstacles, and smoothness while not watching the viewfinder. If shooting video
or with video assist, you can shoot without a finder, then check each take and
then make adjustments on the next take.
For very complicated shots where
the operator canít easily watch a viewfinder, someone else might watch the video
assist and verbally or by radio guide the operator through the shot. The operator
can concentrate on his own body position and that of the camera, such as with
a fisheye lens where not seeing the operator's feet and staying on the set is
a problem. Noting exactly where problems happen during the shot is important
for making corrections on the next take. If it is a sound shot an intercom might
be necessary talk to the operator.
Another application of inertia is
the gyroscope that alone can actively keep a smaller camera stable. Using a
combination of inertial stabilization and one or more Kenyon gyrostabilizers
will provide a very stable system. If most of the camera's stabilization system
is simple inertia, the gyro doesnít have to work as hard and is more effective.
Integrate one or more Kenyons as counterweights and make sure they are rigidly
attached to the camera system. Also make sure the cables attach close to the
CG of the camera system to prevent the cables pulling the camera where you don't
want it to go.
Note. Many equipment manufacturers
and some rental houses exaggerate the applications of their devices. Ask around
before you try to use any device for a new application, maybe there is some
other device that will do the job better and even much cheaper and simpler.
Gyro stabilized systems like Westcam
are beyond my experience and offer excellent stability. They are a bit expensive.
© Copyright 1999-2004 Ron Dexter. All Rights Reserved.