The First Time (1978)

Sue Morris is the long-suffering wife of lazy layabout Jan. He refuses to look for work, so Sue decides to help make ends meet by dabbling in porn videos. While shooting her first flick, she meets Jake Matera, a swinging lawyer who rents his house out as a hardcore set. Jake invites Sue to a swing party, and she brings Jan along for some partner-swapping fun. But what's Sue to do when she finds herself more attracted to Jake than to her own husband?