represents the minimum height of the lettering you can use for a
viewgraph which the viewer can read from the distance stated.
For example, you must find the minimum height of the lettering for a
viewgraph when the projector is 14 feet from the screen and the farthest
viewer is 50 feet from the screen. The dotted line on the chart in
figure 21 shows how you align the straight edge. First you place the
straight edge at the 14foot mark on the left scale, and then align it
with the 50foot mark on the center scale. As you see, the point where
it crosses the right scale is the 1/8inch mark. That is the minimum
height of the lettering you could use for the viewgraph to meet both
Now find the minimum height of the lettering for a viewgraph where the
projector is 30 feet from the screen and the farthest viewer is 60 feet
from the screen. You should find the minimum height of the lettering is
1/16 of an inch for a viewgraph used for these distance requirements.
If you did not find this answer, try again ensuring you align the
straight edge correctly.
(3) Aperture opening. The aperture opening on the viewgraph frame
is the 7 1/2 by 9 1/2inch cutout portion. When preparing the master
for a viewgraph, you must ensure all the lettering and graphics stay
within the aperture area of a viewgraph slide mount. One method to
ensure your work stays centered in the aperture is marking the center
and outer edges of an aperture opening on graph paper, and attach the
graph paper to the drawing surface. Then place the tracing paper over
the graph paper attached to the drawing surface and attach it to the
drawing surface. Since the tracing paper is transparent, you can see
the graph paper through the tracing paper, which allows you to remain
aware of the limits of the aperture opening.
Even the best illustrators make mistakes. If you should make a mistake
when preparing the master, you do not have to make a new master. You
correct the mistake by cutting out the mistake and removing it, and then
inserting a section of tracing paper, using translucent mending tape.
Then all you must do is redraw the area where the mistake was.
c. The Diazo Machine (figure 24). The diazo machine has four
sections: (1) printing, (2) developing, (3) cooling, and (4) exhaust.
(1) Printing section (figure 25). This section of the machine
has four units: (1) light source, (2) reflector assembly, (3) printing
cylinder, and (4) feedbelt. At the start of the reproduction process,
you feed the original and a diazo foil or paper into the machine.