Well, if you had a flir camera looking over your shoulder the tracing effect (caused by localised heating of the screen) would still be there. I actually heard

Well, if you had a flir camera looking over your shoulder the tracing effect (caused by localised heating of the screen) would still be there. I actually heard it is a legit method to defeat pin entry systems. If you can get to the terminal soon enough it was used, relevant keys will be a little hotter than the other. This will be visible with flir. Then all you have to do is figure out the order of digits.