An integrated proximity and ambient light sensor assembly includes an emitter of an IR proximity signal, and a detector configured to detect the IR proximity signal from the emitter when the apparatus is sensing proximity, and to detect ambient light when the apparatus is sensing ambient light. The assembly includes an IR cut filter that has a film disposed over the detector that rejects IR light but passes visible light to the detector, and an opening in the film centered over a midpoint of the detector that passes IR and visible light to the detector. The opening allows IR light to reach the detector from within a narrow angle, but absorbs undesirable emitted IR light that is reflected by oily build-up or “smudge” left on a cover of the device. The film allows visible light to pass for a wider angle to better determine average ambient light.