Against precedent, the Harry Potter film franchise has managed to keep fans of the wildly popular novel series by J.K. Rowling content, despite the many editorial necessities inherent in scaling down the lengthy books into movie-sized installments. Though actor Daniel Radcliffe, who plays Harry in the series, is on the record complaining that the latest film, Harry Potter and the Half-Blood Prince, isn't "dark" enough for him, Radcliffe said that the tonal switch is essential to the overall arc of the films:
I don't think we're holding back, I'm giving my all on the set as I've been brought up to do. But it's true that this is very much a lead-in to the seventh installment, it's setting up the final events, and that's why it might be a harder film to come to grips with. So that's why there are moments where we can be freer, we can have more jokes and a bit more fun with it. You don't always have to think about an immediate danger. Voldemort's not the main source of fear or evil; that's another character.
The decision to cut the seventh and final movie into two installments may have been prompted by financial considerations, but Radcliffe says that it was essential in order to honor the original story:
I'm very happy that the seventh book is being made as two films because I was worried they would have to cut important scenes.... The problem with doing that with the final book is that there is nothing that doesn't relate to the main story or drive it forward. There's not much you could cut. So we've given ourselves the room and opportunity to do it justice.
Harry Potter and the Half-Blood Prince also stars Emma Watson as Hermione Granger, Rupert Grint as Ron Weasley, and Michael Gambon as Albus Dumbledore.