On Monday, the Academy of Motion Picture Arts & Sciences will screen “A Man for All Seasons,” marking the halfway point of its marathon of best picture winners.The Facets of the Diamond program, commemorating Oscar’s Diamond Jubilee, shows one winner each week, chronologically. It began on May 13, 2002, and wraps with “Chicago” on Dec. 8. Yes, the prints are pristine, and yes, the Samuel Goldwyn Theater is the best screening room in town. But really, the fun is in the preshow. Nowadays, moviegoers complain about sitting through 20 minutes of commercials and trailers before the start of a film. But in the 1930s-50s, the preshow included a newsreel, cartoon, trailers and short subject. This wasn’t an era of fast-food filmgoing; an evening at the movies was a full meal. Continuing that tradition, the Acad has a preshow lasting about an hour, including the Oscar-winning cartoon of each respective year, a trailer for the next week’s film, a live-action “newsreel,” the intro of movie participants who attend the screening and footage from the Oscar ceremony. They have everything except an organist and a door prize. The Goldwyn audience includes the usual quota of pale-and-frail film geeks who look like they’d break out in a rash if exposed to direct sunlight. But there are also celebs (from Brett Ratner to Angie Dickinson to Bill Condon), soccer moms, and little old men with their Billy Wilder-style golf caps. One highlight is a half-hour excerpt from that year’s Oscarcast, and anybody who has complaints about recent ceremonies should see this stuff. It’s astonishing to watch host Bob Hope and presenter Gary Cooper impatiently giving directions to the cameraman (“No, you gotta pull way back!”), or see John Wayne greet the host (“Thank you, Bobby!”) and engage him in lame jokes about Indians and Asia. And the sets are often as elaborate and baffling as the women’s hairdos. The plusses? Acceptance speeches were brief and funny, and the shows ran only two hours. There’s also something exhilarating about sitting with a full house that’s roaring with laughter at a cartoon such as “Birds Anonymous,” a spoof of AA in which puddy-tat Sylvester pleads to his sponsor: “I can’t stand it! I gotta have a birdie! I’m weak!” Every week, Randy Haberkamp — whose title is Academy program coordinator of educational and special projects — offers a five-minute presentation in which he rattles off news events of the year on display in order to put the winning film into historical perspective. For example, 1956 (“Around the World in 80 Days”) included references to Nasser, the Suez Canal and “Heartbreak Hotel.” 1964 (“My Fair Lady”): Jimmy Hoffa, the Warren Commission, methadone and the Funky Chicken. Haberkamp’s office at the Acad’s BevHills h.q. is strewn with boxes of programs for past screenings, while videocassettes of past shows are piled high on the floor. Haberkamp has fun working with the staff on the preshows, but he emphasizes that the evenings are really about the films: “One of the fun parts is to show the best print possible.” A primary goal of the series was to show off the Acad’s collection: The majority of the prints come from Academy archives, which has been seriously beefed up since 1990. Soon after he began at the Acad in March 2001, Haberkamp was presented with a plan for the film series but he fought against the idea of double features. The evenings are prepared by him and his fellow workers — “Don’t portray this as ‘The Randy Show’; so much of this is due to them.” It sounds like an acceptance speech. But that’s to be expected: He does, after all, work for the Academy.