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InfraRed Sensitive
Colour Cameras
Ordinary Colour CCTV Cameras are relatively
insensitive to Infrared because they have an IR CUT Filter between
the Lens and Image Sensor, this filter blocks Infrared radiation
with a wavelength greater than ~ 700 nm that would otherwise
adversely affect White Balance, Colour Rendition and Image
Sharpness.
Colour CCTV Cameras that are sensitive to Infrared
either do not have an IR CUT Filter or utilise a special NOTCH IR
CUT Filter that excludes the wavelengths most harmful to colour
quality (720 ~ 830 nm) from reaching the Image Sensor.
A Colour CCTV Camera that does not have an IR CUT
Filter usually has poor colour
rendition characterised by a
Pink-Red
'tint' when the illumination is InfraRed rich,
use of a 'Notch' Filter helps however White Balance,
Colour Rendition and Image Sharpness are compromised
for Infrared sensitivity.
Infrared rich light
sources include Daylight and most Filament type lamps including
common Spot lamps, Tungsten lamps, Halogen lamps, etc.
The majority of Light emitted from 'Cold' type
sources such as Fluorescent, Mercury Vapour, Sodium Vapour, etc., is
visible, these sources contain little Infrared energy.
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