The cinematographer for Harry Potter and the Half-Blood Prince, Bruno Delbonnel, was interviewed by the crew behind The Oscars to promote the sixth Potter films' “Best Cinematography” nomination:
Q: What was the biggest challenge you faced on the movie for which you are nominated?
A: First of all I guess it was to be as good as the previous cinematographers who worked on HP. John Seale, Roger Pratt, Michael Seresin, Slawomir Idziak.
To be as good but different.
Some of the sets are there since the very first Potter. How could I light them in a different way? This question brought another one based on the series itself. It was Potter number six, the story was less about the big fights than the relationships between the characters. Nevertheless the drama is still there and I thought it would be interesting to have those very intimates stories amidst this very dark mood. As if the school was a dark character. That's when I suggested to go for this (again) dark moody variations of grays. Fortunately David Yates, and the producers liked the idea.