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.