(a) Fortunately, a chart exists that you can use to determine
the minimum size of the lettering, based on the two distances (figure 2-
3). This chart has three scales: (1) projector distance in feet, (2)
farthest viewer from the screen distance in feet, and (3) minimum height
of the lettering in inches, indicated in fractions as well as decimals.
(b) The only information you need to use this chart is the
distance the projector and the farthest viewer are from the screen. To
use this chart, place a straight edge at the point on the left scale
(projector distance in feet) that represents the distance the projector
is from the screen and align it with the point on the middle scale
(distance from the screen to farthest viewer in feet) that presents the
distance the farthest viewer is from the screen.
When you have the
straight edge aligned with these two points, the point where it crosses
the right scale (minimum height of letter in inches)