Jonas Mekas has long been a leading advocate for avant-garde film, producing a large body of criticism from the 1950s to the '70s and founding the Anthology Film Archives in New York City. But he's also an inspired and original diaristic filmmaker whose work combines short bursts of images, speeded-up motion, and improvisational in-camera editing. These two shorts, assembled from footage Mekas had shot decades earlier, include John Lennon, Yoko Ono, Andy Warhol, and Jacqueline Kennedy, yet they offer more than celebrity watching. Happy Birthday to John (1996) probes the link between image making and celebrity culture, presenting a flashy rock concert in Madison Square Garden, Warhol shooting Polaroids, and Lennon and Ono baring their butts in a photo session. This Side of Paradise: Fragments of an Unfinished Biography (1999) shows Kennedy, her sister Lee Radziwill, and their children at Montauk, Long Island, in the late 60s and early 70s. It's a series of privileged moments, with the kids' restless energy and sudden movements echoing Mekas's jittery camera; when the children insist on riding on top of a car, dangling their feet in front of the windshield, the presence of the late John Kennedy Jr. only accentuates the painful fragility of the family's play. 59 min. Chicago Filmmakers, 5243 N. Clark, Saturday, June 15, 7:00 and 9:00, 773-293-1447.