Originally Posted by diogen
IIRC, it was never done before. Or since.
Transformers: Revenge of the Fallen did have sequences that were filmed and shown in IMAX. I think it was Walmart that sold a special "IMAX" version of this movie tht also had changing ARs on BD - not sure. The new Mission Impossible will also have this. As will John Woo's Flying Tigers and of course the new Batman movie; The Dark Knight Rises
There have been other films that have used multiple aspect ratios, just not IMAX which isn't done the same way it was shown at an IMAX theater on The Dark Knight. IMAX 15/70 has an AR of 1.44. But for home video, they changed it to 1.78 as it probably wouldn't have looked right and the IMAX sequences would have lost their granduer