How do I detect a change in a 3 frame sequence of images?

I need to detect smoke in a 3 frame image sequence with time difference.

I segmented some suspicious regions in the image. I need a method to detect if there are changes in the region by using frames. I calculated the NCC value of the region between two frames, but need other methods to decide about smoke.

Answer 1

[Sean de Wolski]

how about an image subtraction or absolute difference?

doc imsubtract
doc imabsdiff

[azarm]

well, actually i tried it before. the problem is with compact smoke in close-up range that doesn't chang that much in the sequence. Using diff, the object in some cases would be erased.