An imaging system includes a shutter, an array of photodetectors, and electronic circuitry associated with the photodetectors to read intensity values from the photodetectors, the electronic circuitry including elements configured to provide an operating bias point of the photodetectors. The imaging system includes components, such as a controller, configured to adaptively adjust the operating bias for the photodetectors wherein the adjustment is based at least in part on intermittent measurement of a flat field image. During use, the imaging system can be configured to perform intermittent adjustments of the operating bias based on changes in photodetector values for intermittently acquired flat field images. Adjustment of the operating bias may provide compensation for drift over time of the photodetectors and/or electronics due to effects including but not limited to temperature changes.