What does the Oflow node do? The quick answer is magic. Consider an image sequence consisting of 100 frames, To slow this down to half its speed, then more frames will be required. 100 more to be precise, each one located between a pair of the original frames.
Where does this extra information come from? Traditional re-timing (such as that provided by the Retime node) would make the new frame by blending two neighbouring frames together, like so:
Oflow analyses the content and the motion of the original frames and from this constructs a brand new frame, like so:
Here is what the difference looks like on real footage. See how the Retimed frame is a blend of frames, whilst the Oflow'd frame is a genuine new frame:
Tip: Oflow is very slow to process. It helps to render out any 'Oflow'd' image sequence and then read it back into the script.
There is an example of this node in action in the assets of Lesson 5.