To read calibrated images from a folder that has a calibration file, check the “calibration” flag in ReadImage or ReadStack. The read module looks up the name of each file in the calibration file, gets the mean value of the calibration target, and divides the incoming values by it, producing calibrated data on the fly.
The example shows a PCA computation. The dialog shows that the “input” image is on the left and the “ROI” image comes from the top. Note the small window for the region of interest, and that both ReadStack modules have “calibration” checked. Calibrating the data before analyzing it with PCA may give a better result.