Two very different images - the aging wooden building and the hard-edged stripe of color - show up all the time in popular U.S. art.

Artists by the thousands march in Andrew Wyeth's army. They tend to load their paintings of old barns, sheds and houses with bittersweet nostalgia for the good old days. Comparably numerous are the hard-edge field painters who use parallel bands of color to give their abstract pictures of kind of machined urban flash.

These two opposing images - the wood wall and the stripe - have but one thing in common: Most painters can't resist them. Washington's A. Brockie Stevenson, whose new works are on view at the Fendrick Gallery, 3059 M St. NW, paints both these things at once.

The old buildings that he shows us are the clapboard houses of the coast of Maine. But Stevenson is more than just another regionalist. He is a geometer as well.

Look, for instance, at the house-scape that Stevenson calls Freedman's." The lawn, the cloudless sky and the shuttered windows in the left half of the painting transport one to New England. One can almost smell the breezes from the sea, or the boiled dinner being prepared in the kitchen. But the right half of the picture seems a kind of Kenneth Noland of horizontal bands. "Freedman's" might appear a schizophrenic piectre were not its many elements so tightly locked in place.

Brockie Stevenson is good at that. He is not seduced by details. No weeds choke his lawns, the white paint of his clapboard walls never seems to flake. Instead, his art obeys a kind of mathematics. His views are mostly frontal, his light is flat and even, he is almost always loyal to the straight line and the grid.

Stevenson, who has taught for years at the Corcoran School of Art, seems an exceptionally sweet-tempered man, and something of his gracious warmth is apparent in his art. Though strict, his paintings never shock; though slightly sentimental, they are never syrupy. No wonder people like them.

To wander through his show is to pay a mental visit to a lovely coastal town. Small boats are anchored in the harbor, the architecture is admirable, the red doors of the firehouse have handles of bright brass.

Despite their kindness and their strength, his pictures seem to me, however, not without their flaws. His colors - whites, reds, blues, nd greens - are not exactly subtle, and they sometimes skirt the garish, as in the reds and purples of his "Green Island Light." Though their spirit is precisionist, Stevenson's paintings, seen close-up, seem insufficiently meticulous. His straight lines are sometimes marred by unnecessary blobs.

But these are minor cavils. This is a handsome show. It closes on May 20.

William Dunlap, whose paintings, photos, and collages, are now at Adams, Davidson, 3233 P St. NW. is another gifted regionalist whose views of trees and grazing cattle - and, of course, old sheds and barns - acknowledge abstract art.

Dunlap's hand is sure, and he paints the Southland very well indeed. From across the room, his hills and ponds and fence posts seem almost photographic, but though his subjects are serene, the surfaces of his pictures are astonishingly free.

He splatters paint, he drips it, occasionally he scribbles. Behind that winter sky are ruled lines and arcs. Peer closer, and you see that grassy meadow is sprinkled oot with flowers, but with press-on letters, an M, an X, an O. That flat plane of white seems both a snowy field and a sheet of paper on which the artist jots small notes to the viewer, as well as to himself.

Dunlap's well-made pictures are personal, inclusive. One leaves his exhibition knowing something of his travels ( he often drives the interstates), the football teams he favors, his family, his friends.

Seen from a few inches, Brockie Stevenson's views become just paint on canvas. Dunlap's, when seen closely, become wild and alive. His show closes May 13.

Robert Kushner's "pattern paintings" at the Lunn Gallery next door are happy, whacky, fun. Those who read art magazines know that "pattern painting" is all the rage among those avant-grade critics who have suddenly grown tired of the cold austerities of so much recent art. One such critic, the German Willy Bongard, believes "that we are witnessing a new chapter in art history - possibly comparable, in its importance, to Pop Art."

I wouldn't go that far.

Kushner's art is anything but austere. His soucces hint of Matisse, Japanese Kimonos and Las Vegas motel decorations. Haute couture and funk are also blended in his stew. He sometimes shows us bunnies, red and blue, as if to include kid's art and comic books as well.

Kushner calls his show "Mere Decoration," as if a bit embarrassed by the claims of men like Bongard. Were he a lesser artist, his show might be a mess, with its acorns, lace, and tassels, its neckties and its flowers. But Kushner pulls it off. What saves him are his colors, the freedom of his brush and the mood of easy joy that unifies this exhibit.

The Pyramid Gallery, 2121 P St. NW, is showing Stanley Sporny, a young and very promising painter from Philadelphia in his first show.Sporny, who builds his representational images of strokes of creamy paint, works in what one might call the Edward Hopper-Wayne Thiebaud-early Diebenkorn tradition. His paintings are ambitious. what makes them most memorable is the way he captures the particular look of northeastern urban light.

The finest pictures here show us Philadelphia, that less than lovely city. Sporny shows us its backstreets made bright by brilliant sunlight, and its trolley tracks and cobblestones after a winter evening's rain. Here and there a single brushstroke - a slab of orange that becomes a brick wall bright with sun, a dot of red that is just the color of stoplight - stops the viewer cold.

His eye for light, natural or electric, or the two in combination, is already fine, but his people do not work. There is a cluminess about them that drags his figure paintings down. His exhibition closes May 16.

The Sander Gallery, 2604 Connecticut Ave. NW, is showing works by Larry Fink, who has been going to posh parties and photographing guests dancing, clutching, waiting, grinning, trying to have fun. Fink catches them at moments at which they least succeed. He shows us many grimaces, but few smiles, much loneliness and little joy. Yet his pictures have the ring of truth. He is a very good photographer.

His lighting is dramatic, his compositions complex, his closeness to his subjects frequently unnerving. Though he tends to concentrate on what he calls the "privileged classes," his photographs remind us how sad we appear when we are trying hardest to have a good time. His show closes on May 10.