Definitions and Principles of Inertial Camera Stabilization

Some types of inertial stabilization:

MECHANICAL INERTIAL STABILIZATION: Stabilizing a camera in space using the basic principles of inertia. Steadicam, Tyler Mount, Body Cam, Pogo Cam, Glide Cam, Handy Man, Doggie Cam

BRUTE FORCE GYROSCOPIC INERTIAL STABILIZATION: (Kenyon and Tyler Gyro mounts) Kenyons are being added to many inertial devices with excellent success.

FEEDBACK INERTIAL CAMERA STABILIZATION: Using inertial camera position information to compensate for unwanted movement from the camera support. (Westcam, Gyrosphere,)

FEEDBACK INERTIAL IMAGE STABILIZATION: Using inertial camera position information to compensate for unwanted camera movement by shifting the position of an optical plate within or in front of the lens. (Dynalens, Arri Image Stabilizer, Canon 2/3" Stabilized Video Lenses, and better Mini-DV camcorders.)

FEEDBACK INERTIAL VIDEO CHIP IMAGE STABILIZATION: Using inertial camera position information to shift the image around on an oversize video chip. Used in cheaper consumer video camcorders for stabilization.

This is mostly a discussion of MECHANICAL INERTIAL STABIILZATION.


THE CAMERA SYSTEM is connected by the CONNECTION SYSTEM (CS) to the ISOLATION SYSTEM (IS) which is attached to the SUPPORT SYSTEM (SS). I suggest that you print out "Heavy Camera Horizontal Rig", "Low POV Rig", "Industry Standard Examples", and "Handheld Vertical TEE Rig for Camcorders" and refer to them as you read this discussion. You might skip by sections that are not clear and return to them later. You might also down load and study some of the US patents as referenced.

1. THE CAMERA SYSTEM is a group of camera and counterweight elements rigidly connected and balanced around a CENTER OF GRAVITY (CG). The camera system elements MUST include the camera and 2 separated counterweights (CW). These counterweights CAN include extended film magazines, extended motors, batteries, video assist, viewfinders, video transmitters, one or more Kenyon Gyros or simple inert counterweights if not one of the above elements.

a. There must be 3 separated weights to stabilize a camera system in all 3 axes. More than 3 weights DO NOT add stability and makes a system more difficult to balance about the camera system's CG. (Consider a long camera or sled as two separate weights.)

b. The camera system components should be rigidly connected so that the system can't flex under stress from support system (SS) movement.

c. Weight farther from the CG makes the system the more stable. The farther a weight is from the CG, the lighter it can be for the same effect. Limits for size are clearances such as going through doorways and the operator's body. It is possible to make a device that is so large that it is so stable that the operator cannot easily control it.

d. Weight near the CG reduces inertial stability, but if the camera is close to the CG, lighter weights attached at a distance reduces the total camera system weight. (See Beta Cam/Arri BL Rig)

e. Adjustments to balance the camera and/or counter weights about the CG should be easy to make. Lightweight dovetails are ideal for camera. Adjustments should have stops so a camera or counterweight can't slide off while adjusting. A zoom lens should be securely attached. (See Center of Gravity Test Rig)

f. To find the CG of a camera or non-symmetrical counter weight component, balance it on a round pencil on 3 different sides.

g. Film moving in a magazine can be compensated for by a movable weight that can be adjusted between shots. This weight should move in line with the spindles of the magazine to compensate for the weight of film moving. .

2. THE SUPPORT SYSTEM (SS) consists of a means to support the weight of the camera and isolation systems (IS) and is attached to a vehicle or an operator's body. The simplest support is the human body, but the average human arm is limited to about 8-lb. total camera system weight held away from the body. (Steadicam Jr. ©. Steadicam Jr. DV ©, Pogo Cam) Heavier weights can be held comfortably closer to the body, but heavier camera systems usually need more sophisticated support systems than the human arm.

a. The support system (SS) [Steadicam © Vest or Body Cam © Backpack] should be securely attached to the operator so that there is no movement between the two. A vehicle SS should be securely attached to its vehicle.

b. A means should be provided to "park" the camera system for loading, resting the operator and balancing the system when removed from the isolation system.

3. The CONNECTION SYSTEM (CS) allows the camera system to move freely without unwanted torques from the support system being transmitted to the camera system. The connection system is attached at or near the CG of the camera system. [Gimbal]

a. The simplest connection between the camera system and the support system is the human hand. This works well for some medium weight hand supported devices with extended weights. [Pogo Cam] Light weigh systems like Steadicam Jr. © need more complicated isolation.

b. Except for hand gripped devices like Pogo Cam, friction must be minimal at the connection system between the camera and isolation systems (IS). Bearings allow the camera system to remain stable and not be influenced by support system movements. A fiber cord from an above support attached to the camera system's CG works too. (Patented in Germany in 1927 # 441148) A vertical spike from below resting in a cone in the camera system at its CG is also very simple and works well. (Patented in the 1936's for the Eymo Camera US Patent #2,036,097)

c. If the camera system is attached to the isolation system (IS) slightly above the CG of the camera system, gravity will help keep the camera's horizon level. [Ala Steadicam © US Pat. #4,017,168] The operator must make slight corrections when starting or stopping a move.

d. If the IS is made of bearings, they must be in the same plane. If a pan bearing is not level with the tilt bearings, the unit will fall to one side on its own.

4. The ISOLATION SYSTEM (IS) absorbs the relative motion between the support system and the camera system. This can be a combination of arms, cables, levers and springs. [Steadicam © and Body Cam ©].

a. Steadicam © type systems use a spring and lever arm to support the camera system weight and isolate the operator's walking movements from the camera system.

b. Back pack mounted systems such as the Body Cam © /Body Mount support the camera from over the shoulder with less strain on the torso at the expense of limited overhead and side to side clearances. (US Pat. #4,206,983)

The above two devices each have their advantages and disadvantages. Practice with any device helps overcome disadvantages and develop appropriate the operator's skills.

c. Helicopter mount systems like Nelson Tyler's use massive weights and balance every movable element about its CG to isolate the camera from the helicopter's movements. The vertical post allows the upper camera section to remain stable in space as the helicopter body oscillates around the camera system. (A very simplified explanation of a complex system.) (US Pats. #3,352,521 and #3,457,350)

d. Various camera system designs can be hung from above with springs or bunji cord to isolate the camera system from undesired movement of the support. Those and spike from below systems will be discussed in this site.

5. GUIDANCE SYSTEM (GS). The camera should be guided close to the CG or symmetrically extended from the camera system CG as in the Tyler Helicopter Mount and Body Cam ©. If the camera system is controlled by a force any distance from the CG or not symmetrically in line with it, the camera system will be pushed unequally out of balance when the operator tries to control the camera.

The smaller the guidance point is in relation to the size and weight of the camera system, the less likely the operator is to over correct intentional moves. I have found a 3/8" diameter Allen head screw head (of a 1/4" Allen screw) guided by finger tips ideal for a 4-6 pound human arm supported device. This screw head is also the cone socket where the camera system is supported from below by a spike sticking up in a handgrip. A whole hand wrapped around the post of the much heavier Steadicam © is right for the weight of the Steadicam © camera, post and sled.


Counter-weights should always be working parts of the camera system if possible; batteries, monitors, extended film magazines, motors, extended motors, video transmitters, focus systems etc. The camera and/or counter-weights must be adjustable about the CG to allow for balancing the system. Balancing adjustments at camera or the heaviest element is the most sensitive. If batteries and transmitters are not convenient as part of the camera system, they can be carried on the operator's body and connected by cable. Flexible lightweight power, video and control cables should be attached close to the camera system CG to prevent unwanted torques effecting the camera system.

Adjusting the camera system's CG to the attachment point must be easy to do. It helps to keep every component symmetrical in one plane with the CG and connection system. If you use tube (or pipe), balance every part about the tube’s center. Modified Speed Rail © "Tees" (#5) will do for T shaped devices. Cut a coupler (#70) in two and weld a half to the side outlet of a tee (#5) to give it enough strength. Speed Rail © crosses (# 10 or 30A) join the two pipes out of line in a plane and create an imbalance that is hard to correct. Vibration Dampening Clamps are also useful and come in most pipe and tubing sizes. Make sure adjustments cannot slip under strain.

Front to back and side to side horizontal adjustments are easier to make under load than vertical up and down adjustments. Up and down adjustments can be made easier if the camera is pointed up or down. (If design allows, such as horizontal TEE rig.) Make each horizontal and vertical adjustment independent. Make sure that no camera parts can fall off when adjusting the CG. Consider small movable weights to fine tune larger masses.

The isolation support arms or devices should be as light and flexible as possible. The weight of an isolation system, such as a heavy mechanical arm effectively adds weight to the camera system at the CG of the camera system and reduces inertial stability. A vertical fly fishing rod bent 180 degrees is the simplest and best example of an ideal support and isolation system. It is flexible in all directions has almost no mass, but unfortunately will only support a couple of pounds.

A bunji cord from a high support is also a simple and very light weight isolation system. It could support a very heavy camera system from a high ceiling of a sound stage or crane. The higher the anchor point, the more flexibility the operator has. Primitive, effective but will not impress the on-lookers even it the film looks great. Expect howls of laughter.

ERGONOMICS: Any device should be as operator friendly and interface with the human body as much as possible. Designs should take into consideration clearances of the operator's limbs and the most comfortable operator positions for the camera system. Controls and viewfinder position should be ergonomic. The Tyler Helicopter Mount and Steadicam © are excellent examples.

WIND RESISTANCE AND FRICTION. If a device is involved with wind resistance moving at higher speeds such as on a vehicle, consider balancing surface areas to the wind around the CG and /or support point. Large matte boxes and magazines can be a problem. Use an effects fan to test for aerodynamic balance.

TETANUS: While the human body/brain is a million dollar support and guidance system, the human arm will support only a certain amount of weight before muscles start to fight one another (tetanus) and add instability. The average non-athlete can hold only about 6 to 8 pounds out from the body with one hand and not become unstable. Practice and exercise helps increase this weight limit. Tetanus also increases with general fatigue.

The motions of the operator must be isolated from the camera system as much as possible. A hand firmly gripping a lightweight (4lb. to 8lb.) camera system at a support point can transmit the operator's body movements to the camera system.

The operator's eye should be isolated from the light to medium weight device eyepieces so that the operator's head movements are not transmitted to the camera. This is little problem with helicopter mounts because they are so heavy that a little pressure from the eye doesn't effect the camera system.

So the ideal device has its weights concentrated at its extremities. Every weight is a working part. The camera system's connecting members weigh little but are very rigid. The camera system is well isolated from the support system. The control point is at the CG or symmetrical with it. And the whole thing is ergonomic and easy to adjust balance about the CG.

VIEWFINDERS: Moving hand held camera shots require less exact framing than a tripod, crane or dolly mounted camera shot. The simplest and most reliable viewfinder for an eye level camera is a wire frame. Video is standard with most systems. Some CRT helmet view finders gives a good image in bright light but must be gotten used to. Some LCD finders may still be too dim in bright light and need a neutral density mask to reduce outside light to the eyes to balance the brightness of the LCD image. Emission from a CRT close to the eye and brain is a health concern.


1. The operator should have peripheral binocular vision below the viewing image so he can maneuver his body safely.

2. The helmet should be as light as possible and fitted firmly to the head. The weight of the monitor should be balanced on the other side of the head if possible. This can be done with batteries.

3. The image should appear at or near infinity to allow the operator to shift attention without eye accommodation (distance focus) from his environment viewed directly below the viewfinder image and to the image in the video monitor.

4. The monitor should be viewable in any light.

5. The system should be as compact as possible.

THE PROBLEM WITH HELMET FINDERS: Most people find it impossible to look at two different images at the same time. Some get sick immediately. A good way to avoid this is to practice shooting with both eyes open when operating any camera and shifting attention from one eye to the other. One eyelid can blink closed. While shooting with a regular camera you can watch for things happening out of the frame seen in the viewfinder. This takes practice, but is an invaluable skill. Using the helmet finder then becomes much easier.


Balancing the camera weight about the pivot points of the tripod or remote head increases stability. (See Prof. Rigging / Inertial Tripod Head)

Keeping the operator's eye away from the eyepiece is important to reduce motion from the operator's body.

Operator's comfort is important to allow him to concentrate on framing, focus, performance and judging camera stability.

The ability to pan and tilt to extreme angles easily should be considered. Although the video tap images are less desirable than looking at the ground glass, they are worth trying. A parallax color video camera gives a better image to see detail than a video assist of the ground glass.

A study of the movements of each support vehicle is important. Each has different motion. A helicopter has an oscillating rotary motion as the body of the chopper vibrates below the supporting blades. Balancing the blades is very important. An airplane is very susceptible to disturbances in the air. It gives a tilt and horizon level disturbances if shooting to the side. Both have engine vibration to remove. Dollies and land vehicles have road and track bumps to contend with that tilt the camera if not inertially mounted. These can be reduced by an inertial head and strong support to the vehicle frame or close to the wheels if the body flexes.

The human body walks with a front to back and up and down gate that has to be isolated. The camera and support system makes smooth walking harder. Fatigue and damage to the body are very important issues.

© Copyright 1999-2004 Ron Dexter. All Rights Reserved.