THE AMERICAN portrait painter Joseph Wright was just as talented, and not quite so shiftless, as Gilbert Stuart. Both painted our Revolutionary War heroes, founding fathers, merchant princes and fashionable ladies.

When they went head-to-head, as in their full-length portraits of George Washington, Wright captured a convincing image of a man clearly capable of deep thought and high command; Stuart's is an almost prissy, Parson Weemsish icon.

Stuart became and remains famous, while even art historians may have to pause and think for a moment about which Joseph Wright is being discussed.

Yet this Joseph Wright (1756-1793) is the one who was the son of the famous expatriate sculptor Patience Wright; who was the first American-born painter accepted at the Royal Academy in London; who was a sculptor so well regarded that General Washington sat for him while the sound of the cannons was still ringing in his ears; and who was the first engraver to the United States Mint.

Why does Wright languish in obscurity? "Well, he died young," says Monroe H. Fabian, curator of the Wright exhibition that opens this Friday at the National Portrait Gallery. "At 37, when he died in the Philadelphia yellow fever epidemic, he hadn't assembled a very large body of work. Much of what he did has been lost, and a number of pieces have been attributed to other artists. What remains is scattered; it's largely in private hands and obscure places."

When Wright was from this mortal coil untimely ript, he appeared to be on the threshhold of immortality. It exasperates curator Fabian, who has been hot on Wright's trail for 10 years and has written, in the exhibition catalogue, the only dependable biography of the artist.

"Wright and his wife apparently sent their children out of town, because all three of them survived," he said, shaking his head. "But the parents stayed in their house, which was near the docks where the fever was centered."

Wright's body was hustled off to an unmarked grave and his household broken up with some haste and confusion. Because it wasn't then known that mosquitos carry yellow fever, the victims' clothing and personal effects were usually burned, which is what probably became of Wright's records and papers.

His fame began to fade almost immediately, while Stuart worked (when not in the embrace of his "cheerful bottle") for several more decades, painting so many of our notables so many times that his idealized portraits have become our conception of those who conceived our country.

What was lost with Wright is suggested by what is to be found in this exhibit, whose two dozen paintings represent more than half of the surviving works. First there are his stalwart Washingtons ("a better likeness of me, than any other painter has done," George said, adding that Wright was "a little lazy").

Then there are a dozen other marvelously perceptive and straightforward portraits. Most particularly arresting are those of Frederick Augustus Muhlenberg, first Speaker of the House; and of Benjamin Goodhue, an almost heroically homely gentleman. The Goodhue is "one of the finest American portraits of the period," Fabian says.

It is at least that. And one wonders what 19th-century American portraiture might have been like had Wright left behind enough work to have wide influence on later portraitists. Wright's bold style and uncompromising honesty surely would have left us with a less worshipful and more worthwhile sense of those who launched our ship of state.

The exhibition catalogue, which actually is a biography plus the only complete catalog raisonn,e of Wright, has been delayed in press, so that the fruits of Fabian's scholarly labor may not b available for several more months. It's worth waiting for, and should go a long way toward restoring Joseph Wright to his rightful place.

JOSEPH WRIGHT, AMERICAN ARTIST -- Through June 9 at the Smithsonian's National Portrait Gallery, Eighth and F streets NW (Gallery Place station on Metro's Red and Yellow lines). Open 10 to 5:30 daily.