Types of Projectors.

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

the disk.

(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

crawl devices.

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

of focus.

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.

7.

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.

NOTE:

Use figure 220 to follow the discussion of an overhead

projector.

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