Sometimes the glow of infrared LEDs can be undesirable, especially in military or security applications.
940nm is further from the visible spectrum and is much more difficult to see the source at night. 850nm is closer to the visible spectrum, and it’s much easier to see a dull red glow in darkness.
It is usually wise to stay within this spectrum for security cameras, as the sensitivity of these typically fall off from 850nm to 940nm very quickly.
Click here for 810-950nm options.