Abstract: A thermal or infrared imaging system that is particularly useful to enhance a vehicle operator's perception of surrounding scene features under vision-impaired conditions, e.g., rain, fog, smoke, and the like. Scene radiation is passed to an imaging sensor through a wavelength-selective attenuator that operates to pass radiation in a first wavelength range substantially without attenuation and to pass radiation in a second wavelength range with controllable attenuation. This permits maximum sensitivity to objects in the scene that radiate in the fist wavelength range and controllable sensitivity to objects that radiate in the second wavelength range, whereby the sensor may be prevented from becoming overloaded or saturated by radiation in the second wavelength range while continuing to produce useable image signals of objects in the scene that radiate in the first wavelength range.