LLOYD B. Embry, a Washington painter who died in 1979 at 65, enjoyed a long, busy, successful career as a portrait painter, with a stream of commissions from lawmakers, judges, generals, ambassadors and high-ranking bureaucrats. A different Embry is on view at the Stoneman Gallery this month--a sensitive watercolorist attentive to the crisp light of Cape Cod and the sharp geometries of its architecture.

Embry was born in Washington and showed his talent at an early age. He studied at the art schools of the Phillips Collection and the Corcoran before receiving his bachelor's degree in fine arts from Yale in 1938. Afterward, he turned himself into a competent, perceptive painter of portraits, all the while continuing privately to paint landscapes, cityscapes and figure studies. That he chose not to exhibit these aspects of his work is a bit puzzling, for they are very good.

In collaboration with his family, the Stoneman Gallery has unveiled a cross-section of works by the other, private Embry. The Cape Cod pictures constitute the stronger, more consistent body of work in this show--the Embry family summered on the Cape from the 1940s on and the painter obviously responded to the climate and mood of the place. His special domain as a watercolorist came to be the way light both defines and alters the volumes and surfaces of the buildings there, something that also attracted his friend Edward Hopper.

Embry's indebtedness to Hopper is clear, and his modesty vis-a -vis the work of this master may be one reason he kept these paintings from public view. Embry's works rarely encompass the narrative, psychological tensions that Hopper's paintings habitually evoke. Neither was stylistic or formal invention his forte. Still, the pristine factuality of Embry's images calls for attention. More often than not he cropped the images severely, the better to focus on the contrasts between sunlight and shade, and to study the gray-blue luminescence of shadows cast by eaves or shutters or curtains. Sometimes he concentrated on a single window to great effect, as in "No. 17, Shutters" or upon the flank of a white house surrounded by cool, subtle skies, as in "Cape Shadows" or "Hopper's House."

Embry also painted the nude female figure with an affecting combination of academic correctness and sensual warmth. Not surprisingly, he often painted himself, and something of his intelligence and modesty is told in a sequence of small, objective self-portraits in oil. As a whole, the exhibition makes a welcome, belated tribute. The Stoneman Gallery, 408 Eighth St. NW, is open from 9 a.m. to 5 p.m. Tuesday through Saturday. The show continues through April 30. Jerry Clapsaddle at Montpelier

The title of Jerry Clapsaddle's exhibition at the Montpelier Cultural Arts Center--"Poles: Painted and Installed"--describes the show with the utmost economy but hardly suggests its fine, poetic effect. The exhibition consists of 28 tall, thin, flexible spruce poles, each painted in different colors and patterns and each placed carefully in a big, clean-lined space. Their arrangement creates a curious sense of expectancy. They stand there in a silence you can almost touch.

The piece is a balancing act of contrasting qualities. The poles, bent gracefully in tension between floor and walls, beams or lighting tracks, adhere to the basic rectangular lines of the space, and yet their rhythm is slightly askew and unpredictable. They seem to move through the space, like dancing arcs, and yet they are quite erect and still. Perhaps the most important contrast, though, is between the identity of the poles as punctuation marks in space and as individual paintings.

Clapsaddle, after all, is a painter who has made his name creating works on canvas--abstract works, for the most part, consisting of hundreds of separate brush marks interwoven on a diagonal grid. It takes awhile in the presence of the new piece to realize that it really does consist of 28 paintings, each with four sides, and to see that each side of each pole has been skillfully painted in hard-edge geometrical or irregular patterns.

The Constructivists used painting as sculpture or definer of space and, more recently, so have Sam Gilliam, Alan Shields and Gene Davis (with his micro-paintings), among others. With "Poles" Clapsaddle has added a distinctive note to the tradition. The secret of the piece resides in the extreme delicacy of the balance between the whole and its parts. The exhibition continues through April 22. The center is on the grounds of the Montpelier Mansion near Laurel in Prince George's County, at 12826 Laurel-Bowie Road. It is open from 10 a.m. to 5 p.m. seven days a week.