427-0011-00-10 Revision 140
Copyright © FLIR Systems, Inc.
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Noisy image
A noisy image is usually attributed to a cable problem (too short or inferior quality) or the cable
is picking up electromagnetic interference (EMI) from another device. Although coax cable has
built-in losses, the longer and smaller the cable is, the more severe the losses become; and the
higher the signal frequency, the more pronounced the losses. Unfortunately this is one of the
most common and unnecessary problems currently plaguing video security systems as a whole.
Cable characteristics are determined by a number of factors (core material, dielectric material
and shield construction, among others) and must be carefully matched to the specific
application. Moreover, the transmission characteristics of the cable will be influenced by the
physical environment through which the cable is run and the method of installation. Use only
high quality cable and be careful to match the cable to the environment (indoor or outdoor).
Image out of focus
The cameras have an electronically controlled focus mechanism for use during ongoing
operation. This focus mechanism is controlled through the serial interface or Nexus .
The wide angle lens (35mm) has a fixed-focus lens (focused at infinity at the factory) and the
lens focus is not field-adjustable.
Each camera has a minimum focus distance, as listed in section 8.0
35x140MS Camera
Specifications
). An out-of-focus object may be too close to the camera and within the minimum
focus distance.
Image too dark or too light
By default the 35x140MS cameras use an Automatic Gain Control (AGC) setting that has
proven to be superior for most applications, but a particular installation may require an
adjustment to the AGC settings. For example, a very cold background (such as the sky) could
cause the camera to use a wider range than appropriate. Refer to section 3.5
Configuration and
Control
for information about how to make adjustments to the image generated by the camera.
Performance varies with time of day
You may observe differences in the way the camera performs at different times of the day, due
to the diurnal cycle of the sun. Recall that the camera produces an image based on temperature
differences. At certain times of the day, such as just before dawn, the objects in the image
scene may all be roughly the same temperature, compared to other times of the day. Compare
this to imagery right after sunset, when objects in the image may be radiating heat energy that
has been absorbed during the day due to solar loading. Greater temperature differences in the
scene generally will allow the camera to produce high-contrast imagery.
Image freezes
By design, the camera image will freeze momentarily on a periodic basis during the Flat Field
Correction (FFC) cycle. It is possible to change the interval used for FFC; refer to section 6.2
Flat Field Correction (FFC)
.
