Bi685 is designed for use in certain aerial vegetative health monitoring applications. This filter isolates the 685nm wavelength range used in some red light vegetative health indices When plants are stressed or dying, photosynthesis slows down or stops. IR wavelengths are absorbed, while more visible light–particularly red light–is reflected.

Bi685 filters are also recommended for use with dark red laser diodes and LED lighting operating in the 680-690nm range, particularly in situations where ambient light can be overwhelming or separation from other red lighting wavelengths is needed.