Theatre Design & Technology - Winter 1978 - 10

A Short Method tor Dealing with Viewing
Distance.
Consider the viewing distance always to be 100 units. (If
you use two divisions to the inch, it would be SO"; if three
divisions to the inch, 33'13"; if four divisions, 25"; if five divisions, 20"; if six divisions, 16%".) This makes the math easier
and facilitates the use of an engineer's scale rule (divided in
tenths) in transferring calculations to your drawing.

Figure 8

A NOTE ABOUT SCALE: The relationship between the observer distance and the viewing distance will establish the
"scale" of the finished rendering (that is, the scale of anything which falls right on the proscenium plane). For instance, with an observer distance of 50', you could easily
construct a drawing in 1" scale to be viewed from 50", or in
W' scale to be viewed from 25" (see chart, Fig. 10). Fig. 10
is not intended as a description of all the possibilities, or a
limitation of the available choices. It simply lays out in a
chart the most convenient combinations. It is possible to

obmver
4. (EXTREMELY IMPORTANT) Establish the distance from
which you expect the drawing to be viewed. Frequently, in
other systems, this distance is set identical to the observer
distance, but in scale (a 40' observer distance in 1/2" scale is
a 20" viewing distance in the drawing). This does not have to
be the case, although it is convenient.

The Relationship between Drawing Size and
Viewing Distance.
In general, a picture or drawing will be observed/studied
from a distance at which the entire object can be taken-in
without significant head movement. The angle of comfort
tends to be between fifty and sixty degrees. In practice, it is
wise to consider that the viewer will place his or her eyes
further away from the surface than the picture is wide (Fig. 9).
This is why you will frequently find a "rule" that the observer
distance must be at least as far from the stage as the stage is
wide. If an observer distance is established which is too close
(a "wide-angle" view), the finished perspective will not look
right unless the viewer holds the drawing or rendering closer
than he normally would for comfort.

lS"wide

---drawing-----'~

I
I
I

d' 20"1024"
0

I
I
I
I
~
Figure 9
8

Theatre Design & Technology

viewing

rnea~uring

on rule

draWing

di~fance

16.66'

16.66"

20"

33.33'
66.66'
20'

~C3le

112"
'/.t"

30'

40'
60'
SO'
25'
50'

75'
100'
33.33'
66.66'
50'
100'

!,;3/1
~"

33.33"

50"

Y2"
Figure 10

use any observer/viewing distance in combination with any
scale as long as all s' and d' measurements are made in
scale feet. This would simply make the arithmetic a little
more involved.
5. Establish Horizon-line Height. In some cases, this will be
determined by the circumstances: constructing a view with a
very precise observer position, for example, such as a particular seat in the house or a camera on a particular tripod or
pedestal.
In most instances, however, you will want to be sufficiently
high to view enough of the floor for a good sense of depth,
and for the set to relate to the viewer's everyday perceptions.
Usually three or four feet above stage level is a good standard.
6. Start calculating the positions of key points (Fig. 11). Given
a point on the floor, its distance below the horizon on the
drawing is determined by first dividing the horizon-line height
(s) by the total distance from the observer to the upstage level
of the point (d); then by mUltiplying the result (s divided by d)
by 100 (d', the viewing distance). Note that this step can be
done mentally. Mark off the result on your drawing, using the
scale which corresponds to the viewing distance you anticipate.
USITT/Winter, 1978

Table of Contents for the Digital Edition of Theatre Design & Technology - Winter 1978