Many of our customers ask for Infra Red Night Vision Security Cameras. We believe that this is mainly due to the over-frequent use of the term in internet commerce. The main goal you want to reach is : Identification of suspects.
Infra Red LEDs
These days CCTV Dome Cameras are often equipped with in-built infra red LEDs. These point to a centered area in the camera view and illuminate only that area. Any activity in the border or corner areas of the camera view will not be illuminated. Also - CCD Image Sensors of most low cost cameras calculate their overall light sensitivety and thereby the subsequent opening or closing of the auto iris or shutter, by the overall illumination of the camera view. Since the border areas will be completely dark, the iris will open wider in order to receive more light exposure onto the CCD chip.
What now happens is not rocket science; the suspects face, facing the camera in the center view, which is directly illuminated by the infra red already, reflects far too much light right back into the wide open iris. The face will be over-illuminated and not identifyable.
You think that this is exaggerated? The majority of all footage of low cost Security Cameras with inbuilt infra red, after handing over to the police is not being used. Experts at the police department can see at a glance whether CCTV footage has a chance to prevail in court or not.
DSS Night Vision
Another possibility is DSS, which stands for Digital Slow Shuttering. The intelligent electronic in the camera chip will digitally reduce the shutter speed, whilst at the same time avoiding many of the negative side effects of the analog version of doing this. With this technology the existing light can be magnified up to fifty times and higher.
Practically this means that there needs to be 'some' light in the area, or distant light shining into the area. With better Security Cameras moon light and sometimes even star light will be sufficient.
For installers to be on the safe side when quoting and commiting to certain abilities of the system; I recommend to use DSS night vision cameras, as long as there is any light source like a street light etc. within 100 yards.
Christow Anderson is an experienced Security Consultant in Scotland and has been in charge of security camera system design at a leading UK firm.
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