Crane Terms and Technology

An ARM can refer to the long part of any crane or a whole system. Many units made for remote heads up to a hundred feet in length are called arms.

A CRANE can be a studio unit on a heavy mobile base on which and operator, his assistant and director rides or a lightweight camcorder device. It's often up to the manufacturer what he calls a device.

A LOCATION CRANE such as a Chapman Titan supports up to 2500 lb. of people and equipment up to 27 feet over the ground. It can also hold a much longer arm without an operator behind camera but with a remotely controlled camera.

A JIB is often a shorter arm on which no one rides. A jib can be attached to another arm or crane that allows more complicated moves.

THE (CENTER) POST is a studio term that means the support and point about which and arm pivots.

A LEVELING ARM is a second arm that keeps the camera head level as the arm goes up and down. It can be large and support part of the weight of the camera and counter weight or be smaller and just level the head as a push/pull rod from the middle at the center post bearing to the camera end.

The COUNTER WEIGHT can be lead weights in a BUCKET for a studio crane or barbell weights or sandbags on a lighter DV crane. If the bucket is leveled with the leveling arm, there is no shift in balance of the arm when it is ARMED up and down. If the weights are stationary on the arm and the weight of the camera is not symmetrical about the camera end, there will not be a consistent balance of the camera. This is acceptable for lightweight arms and arms with remote heads.

ALL CRANES ARE DANGEROUS. If a person or gets off a large studio crane without permission from the grips, the remaining operator and camera can be catapulted through the roof. If a counterweight comes off a small camcorder crane, the camera can bean someone its way to the floor. If a tripod collapses under an arm, the whole arm, counterweights and camera meets the floor with the help of gravity.
A crane on a camera car or dolly can provide fast camera set-ups without even doing a camera move. On camera cars, the cameraman, camera assistant and director often ride on the arm for hours knocking off many shots per hour without an arm move.

Some theory:

The mass of any arm, the camera and counterweights stabilize the camera. Inertia provides a smooth acceleration at beginning a move, during the move and deceleration and the end of a move. A well-balanced arm on a camera car provides inertial stabilization. Also any arm attached to a camera will provide a distant anchor that provides resistance to unwanted motions. You don't need "fluid" dampening at the post/pivot, inertia provided dampening. Don't try to move an arm with a gear head at the center post, it will chatter. (See Inertial Stabilization)

Changing the parallelogram linkage can allow some automatic tilts for up to down on the arm for a camera pointing straight ahead of the arm. Someone claims to have patented this feature, but it is very old technology and the claims, if true, are questionable. It doesn't stop you from making one yourself.

Underslung heads and cameras place less strain on the arm's pivots and leveling arms and can provide a lighter arm with the same rigidity.

A camera controlled at the end of an arm with hands on the camera can make some impressive moves and is a good way to learn crane use. The arm keeps the horizon level, relieves the weight of the camera and the inertia of the arm helps make smooth moves. If the tripod/post that the arm is on is on a dolly you get much more freedom of moves, but coordinating the dolly move and arm move becomes s challenge.

Controlling a camera with two hands symmetrically in line with the tilt axis and above or below the pan axis is best. A zoom control convenient to one hand holding the handles is helpful. See pix in Gyro

If moving an arm at its ends seems too sensitive, moving closer to the center post can be smoother. This applies especially to very lightweight arms.

There are many cranes out there with cameras pointing straight off the end of the arm and the tilt controlled by some means, often tilting the tripod head. This allows swinging around in a circle some distance from the tripod and tilting, but panning about the camera axis is not possible and keeping the camera level. High-end professional motion picture arms use expensive and easily controllable remote heads that with training can make the incredible moves you see in movies today. At the low end for lightweight camcorders there are some remote heads using affordable Radio Control parts. Newer radio controls allow fairly smooth starts and stops. Some use cables retracted with springs that work well. They are not cheap.

There is a very simple design when a leveling arm is not necessary. The arm supports the weight of the camera and the camera hangs from a ball joint at the end of the arm. This is useful for shooting close ups at right angles to the arm. Moving the camera in and out helps correct for the limited range of focus when using diopters. (The "Macro Focus" feature on most zoom lenses is of very limited value because they do not allow zooming in the macro position except for the limited range allowed by the auto focus system of the lens. Learn how this feature works before you plan to use it. See Close-Up Photography)

The average mechanic can make a non-leveling arm out of hardware store parts and a ball tripod head. A lot can be learned for little money and lots of practice.

ARM DESIGN: Cables systems like sailboat masts increase stiffness and can reduce weight a lot. One on top of the arm is first priority. Ones on each side prevent side to side bending for faster moves.

Up to a point large thin wall tubing is stronger per foot than smaller thicker tubing of the same weight per foot.

VIEWFINDER The flip-out viewfinder of many camcorders is useful in lower light conditions but not in bright outdoors. Except for some expensive accessory video finders most are difficult to see in bright light. Providing convenient support is also a problem especially if the operator is moving. Helmet finders are disorienting without a lot of practice, but are a good solution. (Check out virtual reality units.) See "Viewfinders…

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