During post production on
Harry Potter and the Half-Blood Prince (2009), he was instructed by Warner Bros. to add more colors to the film, as his extensive use of color grading and de-focussing made it difficult to see things on screen. He and director
David Yates were at first reluctant to do so, as they didn't want to lose the "very European" look that Delbonnel brought to the film. However, after the alterations were made they ultimately were satisfied with the results.