Sample drift is often a problem in single-molecule FRET TIRF-microscopy when molecules drift over distances >1 pixel through the recorded movie.
iSMS can be used to compensate horizontal sample drift when all molecules are subject to the same drift. The program analyses drift using a discrete Fourier transform (DFT) based algorithm for translational image registration between a reference image (an average of a certain frame interval) and all frames throughout the movie. The drift is then compensated by translating all frames in the movie a distance (x,y) defined by the detected shift vector.
Note that drift compensation in iSMS will create a new drift-compensated movie which takes up large amounts of RAM. See this page for managing memory issues in iSMS.
Synthetic drift was originally implemented in iSMS to test the drift compensation algorithm. Now, synthetic drift may be useful for testing and educational purposes.