Why do infrared cameras use 850nm wavelength infrared emission tubes?

The wavelength range of electromagnetic wave with infrared wavelength between microwave and visible light is 750NM-2UM. It seems that infrared wave has the advantages of strong penetration, stability and slow attenuation, and is widely used in remote control, security and detection. The commonly used infrared wavelength is 820NM, which is used for medical treatment. 850NM, safe, 870NM using highway detection, 950, remote control. Why do infrared cameras use 850NM wavelength infrared emission tubes? I can only say that the infrared performance of this band is very suitable for camera requirements. That's all. I am tired and old. I forgot a lot of things.