The analysis process. In this figure, the changes of donor and acceptor images during the steps of the analysis process are shown. DB, DA: donor images before and after bleaching the acceptor; AB AA: acceptor images before and after bleaching (same images as in Figure 1, cropped to fit the page). STEP1: original images; STEP2: images after registration (note the disappearance of the top lines from DA and AA); STEP3: after background subtraction; STEP4: after Gaussian filtering; STEP 5: thresholded images. The corrected FRET/transfer image and histogram derived from it are also displayed.