The optical system of the present invention includes a lens system assembly, a spectral filter material and a pixel array configured such that small, distant, light sources can be reliably detected. The optical system of the present invention provides accurate measurement of the brightness of the detected light sources and identification of the peak wavelength and dominant wavelength of the detected light sources. Use of the optical system of the present invention provides the ability to distinguish headlights of oncoming vehicles and taillights of leading vehicles from one another, as well as, from other light sources.