The enlargement can be set by means of either the foot disk or
an electrical drive with an automatic double coupling (see Fig.7)
uhich disengages the footdisk temporarily. An illuminated en
largement scale on the column of the lens carriage gives the
enlargement factor to tuo decimal places.
The tuo handwheels for the projection table tilts /3 and
are likewise connected to the control system by electrical coup
lings. When the instrument is switched off or the mains supply is
cut they are disconnected automatically, thus excluding the
possibility of accidentally upsetting the Scheimpflug-condition
adjustment of the E4 - particularly through interference with the
servo-control system.
□n the left handwheel panel are the fallowing controls and scales:
The setting control with 0.01 mm divisions for the e principal
point shift, the 3-digit /3 tangent counter with divisions for
reading the fourth decimal place, the switch for setting the desired
table suction area, the main switch and the switches for room lights,
ventilator, scale illumination and vacuum pump.
□n the right handwheel panel are: The control for the e^ principal
point shift, the /3 tangent counter, the switch for opening and
closing the shutter, the lever controlling the electrical drive of
the enlargement spindle and lastly the exposure timer with exposure
button, count down hand, timer interrupter and selector for the ex
posure ranges □ to 18 secs and □ to 180 secs.
For releasing the exposure, a footswitch can be connected to the
instrument as an optional extra. On the E4 there are also outlets
for connections to an automatic exposurementer and to the darkroom
lights.
By rectifying across the diagonals one finds the correct settings
faster than by any other method, provided that the control points
lie near the diagonals, which is usually the case. It is for this
reason that the switch for coupling the handwheels to tilt the table
about the diagonals, which was first introduced with the E3, has also
been provided on the E4. This switch is at the front side of the
base plate within easy reach from the operator's working position.