The 850 nm wavelength is standard for most applications, including CCTV.
The light source does produce a faint red glow at direct exposure, but otherwise it is not visible to the naked eye. Most of the true Day/Night cameras with removable IR cut filter have great sensitivity to 850nm wavelength, that’s why they are so widely used for IR illumination.
The main advantage of the 940nm wavelength is that it is completely invisible.
The light source doesn’t emit any glow. This is imperative for law enforcement, military, traffic and railroad applications where red light can be interpreted as a signal. However, only a handful of cameras are sensitive to 940nm wavelength. The illumination range is 30–40% shorter, compared to 850nm wavelength. While selecting the 940nm IR illuminator, be sure that you really need it, and will be able to use it.
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