Just a friendly reminder that starting this weekend, Harry Potter and the Half-Blood Prince will debut in IMAX theaters, now that the month-long exclusive run that Transformers 2 booked is over.

Since IMAX theaters are typically more expensive (around $15 a ticket), this will probably soften the fall that Half-Blood Prince takes in its third weekend.  The second weekend fell 62% from the first, but BoxOfficeGuru is predicting a 45% drop this time around.  That would give it over $250 million, surpassing the gross of Harry Potter and the Prisoner of Azkaban with plenty more business to go.