Depending on the application, you can place the polarizing disk on the
light (when using a single light source) or directly in front of the
camera lens. You also can apply the technamation principle to fadeins,
fadeouts, color changes, and other effects through manual operation of
(c) Crawl device. A crawl device shows large amounts of
information progressively without losing continuity. This device makes
information crawl or move either vertically or horizontally across the
screen. Television uses vertical crawl devices more than horizontal
A drum crawl is a large cylinder (approximately 48 inches in
circumference) with information attached that mounts on a rod. As you
turn the drum, the information moves and comes into view at the bottom
of the monitor screen and disappears at the top of the screen. The
curvature of the drum gives the information the illusion of rolling in
and out. The center of the information is clear and distinct while the
lines above and below the center appear foreshortened and slightly out
A roller crawl has two rollers approximately 36 inches apart. One end
of a roll of paper attaches to the top roller and the other end attaches
to the bottom roller. With a roller crawl in the upright position, the
information on the paper moves from the bottom to the top of the screen.
If you lay a roller crawl on its side, the information moves from the
right to the left side of the screen or viceversa.
(d) A "gobo." A gobo is a twodimensional part of the graphic
with a cutout area mounted on the front of a crawl device. The cutout
area of the gobo registers or aligns with the information on the crawl.
As the crawl information moves, it appears in the cutout window. An
excellent example of a crawl and gobo combination is a cartoon character
holding a picture frame with information passing through the frame.
Types of Projectors.
Different types of graphics require different projectors to present the
images on the screen. Usually you think of using a projector to show
the images for viewing only. But projectors enlarge or in some cases
reduce the image; therefore, after you have enlarged or reduced the
picture to the required size, you could trace the image instead of
redraw it to size.
Use figure 220 to follow the discussion of an overhead