Spectrophotometric or colorimetric data are normally obtained in some type of photometric unit and must be dealt with mathematically to provide a final result expressedin concentration. Such mathematical operationsare time-consuming, require data transfer, and are subject to human error. A photometric systemhas been devised which can be adjusted to perform calculations automatically and provide direct readout of concentration. This system combines logarithmic conversionof %T with control of both m and b constantsin the straight-line equation, y = mx + b, in which y is absorbance,m is slope, x isconcentration, andb is the blank correction. The systemalso provideslinearizing compensationfor those reactions which do not follow the Beer-Lambert law. The calibration procedurefor the systemis described,as is the linearization of nonlinearstandard curves.