The ER-55 equipment with universal table frame, shown in figure 3,
illustrates a setup for a projection distance of 525 millimeters for use
with vertical photography. These ER-55 projectors can readily be arranged
for use with convergent photography, with provision for satisfying the
Scheimpflug principle. This mode would then be equivalent to the arrange
ment shown in figure 1.
Super-wide-angle cameras have a shorter focal length than conventional
wide-angle cameras and the projection distances of super-wide-angle plotters
are also shorter. Thus the Balplex super-wide-angle projectors (see figure 6)
have a projection distance of only 360 millimeters; this short projection
distance is readily achieved with the universal frame. The Kelsh super-
wide-angle projectors (see figure 7) have a projection distance of 440
millimeters; although the projectors had to be extensively redesigned to
accommodate super-wide-angle photography, no change was required in the
universal frame.
The Wild Heerbrugg super-wide-angle WH-6 plotter (see figure 8) is
similar in principle to the super-wide-angle Balplex but differs somewhat
in its parameters (see Table 1). The projector-and-support assembly of
the WH-6 is so designed that it is compatible for use on the universal
frame.
TRACING TABLE
Figure 9 shows an improved tracing table for use with double-projection
plotters. The fingertip controls for light balance are shown on either side
of the horseshoe base. A provision for a pantograph connection is located
directly below the circular platen. An improved counter contains a graduated
digit wheel, and a system of interchangeable gears provides direct reading
in feet for a variety of plotting scales. This tracing table can be adapted
for use with any of the projection systems listed in Table 1.
9