1. A method for calibrating an imaging system for imaging biological or chemical samples, the method comprising: for each of a plurality of initial effective distances from an optical component of the imaging system to a calibration target at a sample location, identifying an initial optimal focus setting of the optical component, wherein different initial effective distances correspond to different initial optimal focus settings of the optical component; and storing data for the imaging system to determine a first functional approximation that is derived from the initial optimal focus settings of the optical component for the initial effective distances, the data being stored in at least one non-transitory computer readable medium that is adapted to be communicably coupled with the imaging system, wherein the first functional approximation is operable for calculating a new optimal focus setting of the optical component for a new effective distance having a different numerical value that is not a numerical value of one of the initial effective distances, the new effective distance being from a biological or chemical sample to the optical component, the biological or chemical sample not being the calibration target, and wherein the only value input to the first function approximation for calculating the new optimal focus setting of the optical component is the numerical value of the new effective distance; determining a flat-field correction for each of the initial effective distances; and storing data for the imaging system to determine a second functional approximation that is derived from the flat-field corrections at the initial effective distances, the data being stored in the at least one non-transitory computer readable medium that is adapted to be communicably coupled with the imaging system, wherein the second functional approximation is operable for calculating a flat-field correction for a new effective distance that is not one of the initial effective distances, the new effective distance being from a biological or chemical sample to the optical component.