2.
Adjust the back focus by positioning 3. Zoom in to the maximum telephoto
the camera 25-50 feet (7.6-15 m) from position and focus the lens. Zoom out,
a flat vertical surface suitable for
fo-
watching the focus on the monitor. If
cusing. (A textured wall or a page of the image goes out of focus. Repeat
a newspaper are good focusing
tar-
the process until optimum focus is
gets.) Open the iris to its maximum. If obtained. Lock the back focus mecha-
the lens has au autoiris, reduce the
nism in place.
lighting to open the iris up to its maxi-
mum. This is necessary to obtain the
most accurate back focus adjustment.
2.4 Autoiris Adjustment
Autoiris
(AC) zoom lenses must be ad-
justed for optimum picture quality. Al-
though the automatic light control (ALC)
adjustment is provided on the lens, the
level control is preset at the factory and
should not be readjusted unless other
methods of optimizing the picture are
unsuccessful.
Before making any attempt to adjust the
lens, perform the following monitor
setup procedure: turn the BRIGHTNESS
and CONTRAST controls on the monitor
fully counterclockwise, then turn them
back to approximately midscale. These
controls vary from monitor to monitor,
but these settings are adequate for initial
adjustment.
2.4.1 Automatic Light Control (ALC)
This control adjusts the contrast level of
the picture. The limits of the adjustment
are labeled P (peak) and A (average), and
the control is set at average at the factory.
When making an adjustment, turn the
potentiometer a little at a time. If the
contrast is too strong, turn the potenti-
ometer clockwise, toward P; if the con-
trast is too weak, turn the potentiometer
counterclockwise, toward A.
2.4.2 Video Level (LEVEL)
The level control is preset at the factory
for optimum performance, so normally
no adjustment is required. Adjusting this
control when it is not necessary may spoil
the picture quality. If all other adjust-
ments fail to produce a satisfactory pic-
ture, adjust the LEVEL potentiometer.
The adjustment limits are low (L) and
high (H).
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