Few would have anticipated a change from Marcia Hafif. The artist, now in her 70s, was a highly respected monochromatic painter of several decades' standing, and her single-color abstract paintings - made with pigments she ground herself - were intended to inspire calm and concentration. You felt sure there would never be an about-face on the level of Brice Marden's switch from monochromatic panels to the lyrical calligraphic abstraction he's practiced since the mid-1980s.

To those who've paid attention to Hafif's artistic evolution, though, one alteration she made about three years ago still seems bold for a painter who built an international reputation on her single-color canvases and whose devotion to monochromatic painting put her smack in the center of the 1980s "Radical Painting Group."

Out of the blue - or so it seemed - Hafif began combining two colors in her paintings, and quickly launched two series of them. She has since moved on to a third body of two-hued works, "Fresco Paintings," which are being shown at Larry Becker Contemporary Art.

Hafif's new paintings are not frescoes - they're in oil on canvas - but are inspired by the colors in the fresco paintings of the Italian Renaissance painters Fra Angelico and Piero della Francesca, and the relationships between those hues. More often than not, a vertical section of pale blue is a constant, paired with a vertical section of a different width painted in a darker color (including raw sienna, golden green, vine black, and "Italian brown pink lake"). The gallery is displaying five monochromatic paintings from Hafif's 1991 "Table of Pigments" in the back gallery, all featuring heavier, more opaque paint surfaces than her new works, whose transparent paint application dates from her shimmering "Glaze Paintings" of 2004.

Reading about Hafif's work without ever having seen it in person, you might come to this exhibition expecting to experience the impressively formidable restrictions she has set herself during her nearly five-decade career as a minimal, formerly monochrome, painter. But you will likely walk through this show contemplating the endless and marvelous possibilities Hafif has afforded herself.

Look again

There are times when reading a brochure about an artist's work before looking at it really does make all the difference. This is true of Tim Hyde's show at the Philadelphia Museum of Art, which has been granted more space than its "Live Cinema" predecessors - the entire hallway between the contemporary galleries and the Arensberg Collection - and it's particularly true of Hyde's piece

Video panorama of New York

, which most people will interpret as seven filmed views of a blizzardy New York City on seven monitors.

What one learns, reading curator Adelina Vlas' essay, is that Hyde's seven views represent a single video camera's 180-degree sweep over seven hours (divided among the seven monitors, one hour's filming per monitor) during a snowstorm. More interesting, as the snowstorm - which makes the city increasingly less visible - becomes denser, it prevents the camera's lens from focusing. The pulsations one detects in the films are not from wind, it turns out, but from the camera's attempting to translate the views it is trained on.

It's a work that brings to mind Andy Warhol's 1964 film-portrait of the Empire State Building, Empire, as Vlas points out, but presents an even more extreme vision: of time that is not only flattened but also physically divided and extended, of a panoramic view, and of the failure of technology.

Hyde's other video in this show, The Keeper, a single-channel work, also requires explanation, and is similarly rewarding once you know its story - that Hyde had intended to film the courtyard of a former KGB office building in Kiev, Ukraine, but that when he started filming, a woman decided to stand directly in front of him. Hyde went along, allowing his initial idea to morph into a portrait of an unknown woman. You sense the resulting film is all the more unsettling for his lack of intervention.

There are two-dimensional works of Hyde's in this show as well, photographic collages based on sequential photographs of a friend holding pieces of construction material that Hyde then took out of order, cut, and reassembled. They are conceptually intriguing, but mere amuse-bouches next to his videos.