A filter glass with unique spectral transmittance properties has been developed. The glass is composed from oxides of Te, W and Pb doped with CuO. It shows reasonable durability and can be used successfully in the photometric field. The sharp cut-off in transmittance towards longer wavelengths, the complete suppression in the near infrared and the width and symmetry of the bandpass offer exciting possibilities. It would now appear possible that a near perfect standard photopic distribution might be obtained by a monofilter.