The foundation myth of Color Field painting goes something like this: In 1953, two Washington, D.C.-based artists, Morris Louis and Kenneth Noland, paid a visit to the New York studio of Helen Frankenthaler, where they saw a work in which highly diluted oils soaking into the weave of unprimed canvas had caused a beautiful stain effect. Ms. Frankenthaler called the work “Mountains and Sea,” and she had painted it the year before, when she was just 24. Louis later described it as “the bridge between Pollock and what was possible” — and what was thought possible, for him and other artists, is the subject of an important show on view at the Smithsonian American Art Museum, “Color As Field: American Painting, 1950-1975,” superbly curated by Karen Wilkin.

Jackson Pollock dripped and flung paint; Ms. Frankenthaler poured. Yet to her artist visitors, and to the critic Clement Greenberg, who had brought Louis and Noland to Frankenthaler’s studio, and with whom the Color Field painters were from the start associated, Frankenthaler’s approach seemed to offer a fresh way past what Greenberg called the “standardization” of Abstract Expressionism. He termed this new style Post Painterly Abstraction, although, as he acknowledged, it was at times painterly and was never a reaction against Abstract Expressionism.

Thus, there are no easy definitions of the style. The exhibition begins, appropriately, with a handful of Abstract Expressionist artists who influenced the Color Field painters: Adolph Gottlieb, Hans Hofmann, Robert Motherwell, Barnett Newman, Mark Rothko, and Clyfford Still, all of whom were concerned with, among other things, all-overness, the notion that every part of the canvas was of equal importance.

To paraphrase the exhibition’s wall text, the Color Field Painters who followed were committed to the “primacy” of color, to “frontality” — meaning that they deployed their imagery close to the picture plane; their work was flat — and to avoiding the sort of emotional or expressively gestural handling of paint common to many Abstract Expressionists and known as the “Tenth Street touch.” In a sense, Louis and Noland represent the two directions in which such aesthetic commitments might lead. Like Frankenthaler’s, Louis’s diaphanous layers of pigments presented a soft, open field of colors, while Noland took the route of hard-edged abstraction defined also by pure hues and clear design. However, both men (and Frankenthaler as well, starting in the later 1950s) employed acrylic paints (then a new product), which diluted better than oils, allowing for colors at once strong yet thin.

“Floral V” (1959-60) exemplifies Louis’s softer avenue. Translucent bands of color — violets, purples, blues, yellows, etc. — stream upward from the bottom of a large, rectangular canvas, obscured in the bottom two-thirds by an anvil-shaped veil of black pigment. Jules Olitski also opted for buoyant fields of diluted pigments in, for instance, “Tin Lizzie Green” (1964), where a swathe of almost metallic, aqua-green pigment unfurls between two horizontal red bands.

A miasma of bright and darker greens on a vertical banner, Sam Gilliam’s “Green Web” (1967) takes on some of the swirling and pulsating qualities of its era’s psychedelic art. Yet this direction seems to gutter out in Larry Poons’s “Yellow and Brown Womb” (1972): No longer light or buoyant, the pigments here resemble candle-wax drippings mixing uneasily in a morass of yellow, magenta, purple, and brown. Ironically, though one might certainly call it ugly, the painting’s sin is decorativeness — its inert compilation of effects fail to catalyze a reaction; it fails to suggest something beyond its effects.

Color Field painting always risked decorativeness, and that’s one of its strengths. At its best, a work in this style nuzzles that line between art and mere decoration, but doesn’t cross it. Consider a Kenneth Noland target like “Earthen Bound” (1960), a red circle inside a white band defined by a yellow line, all floating on a purple ground: The lucid design might ossify into poster-art décor were it not for the choice of colors and the hand-drawn quality of the shapes presented.

A black circle enclosed in a flood of blue pigment and offset by a small red circle, Olitski’s “Cleopatra Flesh” (1962) nods to Noland’s strong design, while avoiding dead decorativeness by retaining some of the randomness, the natural quality, of the poured-pigment technique. Paintings such as Poons’s “Han-San Cadence” (1963), an irregular pattern of daubs arrayed across a yellow expanse, and Sam Francis’s “Blue Balls” (1960), a pattern of irregular, liquid blue marks on a light blue wash, also balance the chance results of pours and splotches against the stasis of rigid design.

Frank Stella chose to tread the mined decorative frontier with ruler-edged, geometrically precise fields of solid color. And in works such as “Moultonville II” (1966), he pushed all-overness to its logical extreme, eliminating the ground and shaping the canvas to the contours of the forms depicted. Doing so would seem to eliminate not just “touch,” but all emotional engagement, and at times this approach resulted in work sufficiently bland and inoffensive to decorate corporate lobbies across the world.

But these are the wagers of art. The artists in “Color As Field” decided to restrict their means only to those effects specific to painting — color, flatness, a two-dimensional form. And as this gorgeous show proves, the pressures of restriction can produce diamonds indeed.

Until May 26 (8th and F streets N.W., Washington, D.C., 202- 633-7970).