The slit scan technique is simple: you take one column of pixels from a moving image (for example from a webcam). You do this say 20 times per second and put all these columns next to each other. This gives an ever growing image like the one above. Every column of pixels in this image is taken of the exact same spot, but they are all taken at a different point in time. The video shows a screen capture of the tool I built in OpenFrameworks.
The next steps will explain how to install that tool so you can play around with slit scanning yourself.