The title refers to a technique for filming night scenes in broad daylight, achieved by either lowering the lens aperture or through the use of filters.
A sequence uses a scene with a cat drinking milk from a discarded room service tray from Truffaut's film The Soft Skin as its inspiration, this time showing the audience the multiple takes required to get the cat to go to the tray and drink
When director Ferrand listens to a piece of music prepared for the film-within-a-film by George Delerue, he is listening to a piece from Two English Girls
François Truffaut, an early contender to direct The Stunt Man, borrowed elements from that films's source, the Paul Brodeur novel of the same name, for this film's story.
As Severine (Valentina Cortesa) has more and more trouble remembering her lines (blowing several takes), Ferrand eventually writes her lines on pieces of paper that can be stuck up on the set out of sight of the camera, so that she can read them. It doesn't really work here. However, Truffaut used the same trick for himself when he was having trouble remembering his English lines in Close Encounters of the Third Kind.
As the director Ferrand (Francois Truffaut) and the Cinematographer Walter (Walter Bal) are looking over promo stills of Julie Baker (Jacqueline Bisset), one remarks that he remembers her "from that movie with the car chase". This is an inside reference to the fact that five years earlier Bisset played the role of Steve McQueen's girlfriend in Bullitt (1968), a film featuring a groundbreaking car chase.
While the director is listening to music play back over the phone the image shows several books being stacked. All the books are about well know directors including Howard Hawks, Alfred Hitchcock, Luis Buñuel and Jean-Luc Godard.
The film was nominated for Academy Awards for two years: As best foreign language film in 1974, and director, supporting actress (Valentina Cortese), and screenplay in 1975. This happened because the eligibility periods for foreign language film is different than other awards, and is dependent on the film's release in its originating country. Academy rules have since been amended, limiting nominations in all categories to the same year.
François Truffaut's reason for his character Ferrand wearing an earing-aid (while never clearly defined as deaf) is partly expressed in a voice-over mentioning a film director is the person everyone in the crew has a question to ask. In later interviews, Truffaut explained the best way he could find to ignore some of those questions was to pass for someone hard of hearing.
When Nathalie Baye first heard that Billy Wilder asked François Truffaut if he used a real script girl for the part of Joelle, she felt a bit offended as she was trying hard to be a proper actress. Later, she eventually admitted it was the best compliment she could receive.
In joke: While talking about Julie Baker (the American film star portrayed by Jacqueline Bisset), one of the characters says he remembers her from the "car chase" movie - a reference to Bisset's role in Bullitt.
Jean Seberg was first choice for the role of Julie Baker but as the offer failed to reach her, the part eventually went to her co-star of Airport, Jacqueline Bisset.