GE Interlogix KTC-115CC, User Manual, Page: 11 / 14

KTC Compact Cameras Making Additional Adjustments
1040206A / December 2002 11
6 M
AKING
A
DDITIONAL
A
DJUSTMENTS
6.1 S
ETTING THE
A
UTO
I
RIS
L
EVEL
If you are using a plug-in, auto iris, DC-type lens, it may be necessary to
make adjustments to the direct drive level to achieve a good picture in all
light conditions. Use a screwdriver to rotate the direct drive auto iris level
adjuster (Figure 1) to the setting appropriate for your light conditions.
6.2 A
DJUSTING THE
B
ACK
F
OCUS
Back focusing ensures that the image remains sharp and crisp under
varied lighting conditions. It takes into account changes in the lens’ depth
of field and is used to match the lens’ back focal length with the camera’s
imaging device.
Depth of field is the proportion of the field of view that is in correct focus.
Depth of field will decrease when the focal length is long, the f-number is
small (iris fully open), or the object distance is short.
To achieve correct back focus, adjustments should be made only under
the following conditions:
•
In low light—at night or in simulated low-light conditions.
•
When the depth of field is at its minimum. The lens’ depth of
field is most narrow when the iris is fully open.
To adjust the back focus, perform the following:
1) Operate the camera and view an object approximately 75 ft away.
2) If the lens has a focus ring, set it to infinity by turning it fully
clockwise as viewed from the front of the camera.
3) If the lens has a manual iris, set the lens iris adjustment to the
widest opening or lowest f-number. If the lens has an auto iris,
place a filter in front of the lens to simulate low-light conditions and
force the iris to open fully.
4) Unscrew the back focus adjustment lock screw to ensure that the
back focus adjustment ring turns.