When the Chinese guy is shooting at Indy, Indy and Willie (Sp?) are behind a stone that's rolling. When it gets to the wall, Willie and Indy jump out the window. When Indy is falling, his coat goes from brown (the farther away shot of the stunt double) to white (the close up of Harrison Ford). It is very obvious and you needn't watch it frame by frame. In fact, I caught this while watching it on TV.