def unitResponse(self, band):
        """Put a flat spectrum of 1 photlam through this band and integrate.
        This is used internally for :ref:`pysynphot-formula-effstim`
        calculations."""
        #sumfilt(wave,0,band)
        # SUMFILT = Sum [ FILT(I) * WAVE(I) ** NPOW * DWAVE(I) ]
        total = band.trapezoidIntegration(band.wave, band.throughput)
        return 1.0/total