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
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
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
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.