Over a half century Stan Brakhage has come to be regarded as our most significant avant-garde filmmaker, admired for the way he explores the plastic, rhythmic quality of images (most of his films lack sound tracks or obvious narratives). The six masterpieces on this program come from different periods in his career, but they all retain their vibrancy by undercutting our expectations, even violating their own patterns or structures. Making its Chicago premiere is the hand-painted series Interpolations 1-5 (1992), whose full 35-millimeter frame allows for more detail and diversity than Brakhage's customary smaller film stock. In the first section, multicolored blobs contrast with fuzzy photographed lights; in the third, flickering specks become hundreds of tiny rods and later cracks in paint. Rhythmic complexity has long been a characteristic of Brakhage's work, but the series takes his polyrhythms to new heights by creating different movements in different portions of the frame; there's a sense of shapes being generated and reabsorbed in a cosmic vision of eternal change. In Visions in Meditation #2: Mesa Verde (1989) the black entrances to the famous Colorado cliff dwellings suggest voids in human understanding, and in Murder Psalm (1981) an industrial film about epilepsy becomes a horrific vision of our repetitive and reductive mass culture. Also showing: Dog Star Man: Prelude (1961), Yggdrasill Whose Roots Are Stars in the Human Mind (1997), and The Lion and the Zebra Make God's Raw Jewels (1999). 93 min. Gene Siskel Film Center, 164 N. State, Thursday, April 25, 6:00, 312-846-2800.