Both systems demand that the beer be free of turbidity prior to the measurement at 430 nm. In the SRM a second measurement is taken at 700 nm. If the absorption at this wavelength is less than 0.039 (this number comes from ) times the absorption at 430 nm the beer is considered turbidity free. If not, it is to be filtered or centrifuged and the reading repeated. If the ratio test is not passed after clarification then the beer does not have "average spectral characteristics" and, technically, is not qualified to be characterized by the SRM method. The augmented SRM method described below removes this difficulty.