The invention relates to a calibration method for reagent card analyzers, the method comprising the steps of advancing a reagent pad (108a-n) through a plurality of read positions (132a-n) in a field of view of an optical imager (126); detecting by the optical imager (126) optical signals indicative of a reflectance value of the reagent pad (108a-n) at the plurality of read positions (132a-n); designating, by a processor (118) executing processor executable code, at least one of the plurality of read positions (132a-n) as a reference position; calculating, by the processor (118), a set of position-correction factors for at least one of the plurality of read positions (132a-n) other than the reference position by using the optical signal detected at the at least one of the plurality of read positions (132a-n) other than the reference position and the optical signal detected at the reference position; and storing, by the processor (118), the set of position-correction factors for the at least one of the plurality of read positions (132a-n) other than the reference position in a non-transitory computer medium.