Installation Instructions
CDR Series
25
RESIZE WINDOW
USE ARROW KEYS
PRESS SELECT WHEN DONE
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MOVE WINDOW
USE ARROW KEYS
PRESS SELECT WHEN DONE
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BLC (BACKLIGHT COMPENSATION)
The size and position of the centre window is adjusted from the BLC menu by selecting
CENTRE and the RESIZE or MOVE parameter.
Each of the four peripheral windows has an adjustable weighting (0-15) used to determine
its contribution in setting the overall exposure of the scene. A weight setting of 0 means that
the area within the window will not be used to set the overall scene exposure. The weighting
of the centre window is fixed.
The area enclosed by each window is multiplied by its weighting to give an exposure value
for the window. The sum of all five windows is used to calculate an overall exposure value
which is then used by the cameras exposure control circuit.
Example 1.
People entering a shop through the doorway are to be monitored. Without backlight
compensation, a person entering the shop would be seen in silhouette because the relatively
bright windows to each side of the door would cause the camera to reduce its exposure.
By carefully using the backlight compensation facility, it is possible to size and position the
centre window around the area of interest, i.e. the doorway. By setting the weighting of the
four peripheral windows to zero, only the centre window will be used to calculate the scene
exposure. Therefore a person entering the shop will be clearly displayed.
Example 2.
The camera is required to observe a typical street scene. The sky above the buildings in
the street is very bright thus causing the cameras exposure system to adversely
compensate. Using the backlight compensation feature, position the centre window such
that the remaining Top window covers the sky area. The weighting of the Top window can
now be set to zero so that this area does not affect the exposure. The remaining windows
are set to 15. By using this method the buildings and street will be correctly exposed.
Note
The backlight compensation feature will only work with manual lenses when the shutter
speed is set to 1/50 or EI ON. If any other shutter speed is selected and BLC is then
activated, the cursor will automatically jump back to the shutter speed menu item and set it
to 1/50. Conversely, if BLC is switched ON and the shutter speed is then set to anything
other than 1/50 or EI ON, the cursor will automatically jump to BLC and set it to OFF.
The BLC feature will work with both DC (Direct Drive) and video drive Auto-Iris lenses.
