Yoo Ji-tae's character Sang-woo is a sound engineer. Because of lack of prior experience, he had to spend 3 months to learn how to use the machines shown in the film.
Director Hur Jin-ho and actors Yoo Ji-tae & Lee Young-ae would have frequent discussions on set in order about their characters and finding the right emotions within the scene being shot. It's described by Lee Young-ae as solving mathematical formulas, in which they have figure out these difficult answers.