IR Illuminators and LEDs for Day/Night Cameras

Here’s some tidbits about infrared (IR) LEDS used with day/night cameras.  Most, if not all, residential/consumer-grade IR LEDs will emit an electro-magnetic wave in the visible spectrum, meaning  that once it gets dark and the IR LEDs turn on, there will be a visible red glow radiating out of the camera or IR illuminator  This glow is very similar to the red light produced by heat lamps seen at some restaurants, bathrooms, and reptile tanks, minus the heat, of course.  These IR LEDs will have a wavelength in the 750 to 800 nanometer range, which would be perceived by the human eye.  The dome-style day/night camera pictured here from Seco-larm would produce a visible red glow.  And so would this  camera from Channel Vision, whose price, by the way, has been greatly reduced.   Once you get beyond 850 nm, the red glow begins to disappear.  Get past 940 nm and it becomes invisible.  Searching on-line, I’ve come to this generalization…if the manufacturer does not specify the wavelength of the IR LEDs in their product literature, chances are that there will be a visible glowing of the LEDs during night ops.  The sites that did have ”invisible IR” clearly stated the use of 940 nm LEDs in their documents.