The locker-room quiz
Troeltsch pretends to shuffle cards. ‘Next item. Next like flash-card. Define acutance. Anybody?’ ‘A measure of resolution directly proportional to the resolved ratio of a given pulse’s digital code,’ Hal says. ‘The Incster has the last word once again,’ says Struck. Which invites a chorus: ‘The Halster.’ ‘Halorama.’ ‘Halation.’ ‘Halation,’ Rader says. ‘A halo-shaped exposure-pattern around light sources seen on chemical film at low speed.’ ‘That most angelic of distortions.’
Context
The theme's locker-room set piece: quiz answers on lens pathology sliding into Hal's own name — Halster, Halorama, Halation — until Rader's textbook definition lands and somebody caps it with the angelic-distortion line. JOI's professional vocabulary surviving as his son's flash-card answers, and the son himself renamed as a halo-shaped exposure error: the book's whole Hal-as-optical-phenomenon argument in nine lines of towel-room banter.