Oz the Great and Powerful (2013)

Sam Raimi's prequel tips its hat to The Wizard of Oz and then goes one better. The Kansas prologue is in black and white and a boxy 4:3 frame; when Oscar arrives in Oz, color floods in and the image extends to widescreen at the same moment. The rest of the movie is an uneven family fantasy, but that opening transition is one of the clearest demonstrations of the idea in a modern blockbuster, and a fun one to show anyone who has never noticed a frame change before.