OPERATION OF OPTICAL SYSTEM
THE SPOT SIZE CONTROL HANDLE (“trombone”) is located on the right-hand side
of the spotlight housing just above the base pan. A variation of spot sizes in a ratio of 5:1 can be
obtained with the movement of the Spot Size Control from one extreme to the other.
THE APERTURE SELECTOR (“iris”) is the front handle projecting through the top of
the lamphouse cover plate casting. When this handle is to the left (viewing spotlight from the rear), the
largest aperture is open. Smaller apertures are obtained as the handle is moved to the right.
THE SPOT FOCUSING CONTROL KNOB is located on the lower right side of the
optical system base pan, toward the front of the unit. This control is used to adjust the optical system
for the length of throw. A nominal (“average”) setting of this control can be made by positioning the
aperture selector (iris) handle to the right, and sliding the spot size control (trombone) to the extreme
front. Then rotate the knob until the sharpest white light is obtained on the projected spot. If the
spotlight remains at a given throw point, the focus control can be set to best sharpen the edge of the
projected spot.
MAXIMUM “FLOOD” SPOT is obtained by opening the aperture selector (iris) by
moving its control handle to the left, and sliding the spot size control (trombone) to its extreme rear
stop. If projecting a flood spot for a prolonged period, it may be desirable to adjust the focus control to
sharpen the edge of the spot.
SMALLER SIZED SPOTS are projected as the spot size control (trombone) is moved
forward. Most commonly used spot sizes (head-to-foot “body” spots) are produced with a large aper-
ture (iris open) and a small spot (trombone forward).
FOR A “HEAD” SPOT, or any spot smaller than can be obtained with the spot size
control (trombone) in the extreme forward position, shift the aperture selector handle toward the right
to close the iris and project a smaller spot. The aperture selector handle should always be returned to its
extreme left setting before the spot size control handle is again moved to project larger spots.
A “DIFFUSED” SPOT is projected by pulling the spot size control (trombone) back
toward “flood” setting while closing the iris (aperture selector handle toward right). A “diffused” spot
is seldom required, and is a “soft” edged spot with low light intensity.
THE MASKING SHUTTER AND DOUSER HANDLE (“chopper”) is the rear lever
projecting through the top of the lamphouse cover casting. The masking shutter (chopper) blades are
operated by this lever to shape the projected spot to a rectangle, a light strip, or to douse the spot for
blackout. When the masking shutter control lever is to the extreme right, the chopper blades are open,
and a round spot is projected. Varying degrees of top-and-bottom masking, to complete douse (light
cutoff), are obtained as the lever is moved to the left.
TR4/002
Summary of Contents for 45004-1,2
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