The 850nm wavelength is standard for most security and other applications where a camera requires additional lighting. The 850nm light produces a very faint red glow at its source, but otherwise it is not visible to the naked eye. Most of the true Day/Night cameras with removable IR cut filters have great sensitivity to 850nm wavelength IR, that’s why they are so widely used for IR illumination. Overall the 850nm has an excellent range vs. visibility ratio hence it is ideal for most security and camera lighting applications. The main advantage of the 940nm wavelength is that, in most cases, it is completely invisible to the human eye. This is an imperative for law enforcement and military applications where covert operation is essential to mission success and safety. Traffic and railroad applications also benefit from 940nm wavelength because the red glow can be falsely interpreted as a signal. Only a handful of cameras are sensitive to 940nm wavelength and the range is about 40-50% shorter than 850nm is. We recommend when selecting a 940nm IR illuminator to be sure that your application really needs it and that your camera is capable of recognizing it.