The width of the light beam is controlled by the knobs on the side of the lamp arm nearest the bottom.
The height of the beam is controlled by the knob near the top of the illumination tower. The height of the beam is shown in the small window
above the height control knob. (On
some models there is a lever below
the filter lever which adjusts the
beam height.) The lever between
the height control and window is used
to put neutral density filters, cobalt
and green filters in the light beam.
The top portion of the light tower
rotates the light beam. The post that the height adjustment knob is on can be grasped to rotate this part of the tower. The amount of rotation is noted on the scale at the position of the metal rod below beam height control. This is useful, for example, in measuring the rotation of toric contact lenses.
