An apparatus and method are presented for the analysis of materials. The apparatus includes two or more similar analyzers, with the output of the analyzers combined to provide improved measurements. The apparatus may be, for example, a differential photometric analyzer, such as the AETHALOMETER®. The apparatus and method includes providing flows to the analyzers such that the rate of accumulation per filter area differs for the two or more analyzers. The output of the apparatus or method may be a concentration, such as the concentration of black carbon particulates. Additionally, the output may be an optical measure of particulates that is useful for characterizing the source or history of the particulates.