Continuity: At the end of the film, we see Dick leave an evening fashion show party to join Jo at the church for the final dance. But a hazy filter once the church scene begins can't hide the fact that it was shot in broad daylight (complete with blue sky), even though it should still be evening.
Continuity: When Maggie leaves the Professor's inner sanctum, she leaves her beret on a bust by the door. When Jo goes to leave, the bust and the hat are gone.
Factual errors: In the darkroom scene, the print is left in the fixer for an insufficient amount of time; an experienced photographer, like Dick Avery is supposed to be, would not make this mistake.
Factual errors: When photographing in the book store, the assistant does not pull the dark slide far enough out of the 8 x 10 film holder to expose the entire sheet of film.
Factual errors: In the darkroom for the second print a partly covered paper is exposed, but after developing a full format print is taken out of the bath.
Crew or equipment visible: After Dick kisses Jo and leaves the bookstore, Jo begins to sing "How Long has This Been Going On". As she sings to herself while looking at the mirror in the supposedly empty bookstore, you can clearly see someone moving around on the second floor of the bookstore reflected in the mirror.
Continuity: When Dick leaves the first meeting with Duval to fetch Jo from the café, he says he will have her there at 10 o'clock the next morning. He later tells Jo that she needs to be there at 10:30, which would make her late twice in a row.