3. BLC (backlight compensation) ON/OFF Switch
If the subject you wish to view is too dim because of a bright background, set the BLC
switch (Pole 3) to ON to compensate for the bright background.
With BLC on, the background brightness may saturate in some cases. This
function may not operate properly if the object is too small compared to the area of the
background. This function can be used with either the linear shutter (EE or ELC mode)
or an autoiris lens (AI lens or ALC mode).
WITH BLC OFF WITH BLC ON
4. ALC/ELC select switch
This switch is used to select EE (electronic exposure) or ELC (electronic light control)
mode or AI (autoiris lens) or ALC (automatic light control) mode. Pole 4 is set to ON for
EE/ELC and OFF for AI/ALC.
In the EE/ELC mode, a continuously variable electronic shutter is employed to
automatically control the exposure time of the CCD image sensor according to the
incoming light level. With this mode selected, a fixed or manual iris lens can be used
instead of an autoiris lens. In the AI/ALC mode, the CCD shutter speed is fixed to 1/60
(1/50) sec, and the incoming light level is controlled by the autoiris lens.
To use a video-drive type or the DC-drive type of autoiris lens, set this switch to the
ALC position.
Cautions :
1. Under bright lighting conditions such as outdoors, use an autoiris lens because the
EE/ELC control range is not wide enough under these conditions.
2. Under certain unique lighting conditions, the following phenomena may appear:
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