A system and method for automatically and quantitatively determining the optimal dilution of a reagent is provided. In one embodiment of the claimed method, a plurality of dilution sets are received, where each of the dilution sets consist of a different respective dilution value and a respective plurality of immunoassay staining intensity values. A respective dynamic range metric is determining for each of the plurality of dilution sets relative to the respective plurality immunoassay staining intensity values. Having found the respective dynamic range metric, a dilution set having the numerically optimal dynamic range metric is selected and the dilution value of that dilution set is selected as being representative of an optimal dilution level of the reagent for use in a quantitative immunoassay. In one embodiment, a system is provided with a microscope, an image sensor, and processor module configured determine an optimal dilution of a reagent for use in an quantitative immunoassay.