As far as Jack Boucher is concerned, if a building is 12 1/2 degrees out of plumb, it should stay that way; if there's a chink in the plaster, it should stay there.

"We do not photographically redesign the building," says Boucher, architectural photographer for the Historical American Building Survey for 25 years. "If there is a crack in the wall, we will not retouch it. If there's something damaged or missing, we will not change the building."

Boucher is a stickler for detail and documentary integrity in photographing buildings: "It is a document of the building as it appears, for better or for worse," he says.

But a dumpster out back is another matter.

"I want the pictures to emphasize the buildings, not the distractions," Boucher says. "I will go to great pains to eliminate trash cans. I will wait until the sun comes out from behind a cloud. I will wait until a pedestrian walks out of the scene."

From "better" buildings to "worse" buildings, from one-seat log privies in Wyoming to Frank Lloyd Wright's Kaufmann House in Mill Run, Pa., Boucher has turned his camera lens on almost 6,000 structures in 49 states (Alaska's the missing one), Puerto Rico and the Virgin Islands.

The nearly 55,000 photographs (mostly black and white) he has produced constitute almost half of the Building Survey's collection; 130 of them are on display at the American Institute of Architects. "A Record in Detail: The Architectural Photography of Jack E. Boucher" continues through May 2.

Boucher uses a large-format view-camera to minimize distortion and capture the smallest detail of his subject -- be it a knocker on the front door of the David Ogden House in Fairfield, Conn., or the fac'ade of Paramount Theater in Oakland, Calif.

Bill Lebovich, architectural historian at the Building Survey and the curator of this exhibition, says Boucher "conveys the essence of a building through an isolated detail of an exterior or room."

"I have a tendency to do more detail photography [than most]," Boucher says. "In fact, when I came to HABS in 1958, most of the HABS photographs were general views of entire rooms and buildings -- very few detail views . . . I get in very close to [the subject]: to show the grain of the wood, the detail of the craftsmanship."

But he gets the overall views, too, and that takes the same kind of patience as getting the detail shots. It means waiting for just the right moment.

"There are more pictures in this exhibit where people have just walked out of the view of the camera than you can shake a stick at," Boucher says. "Or a car has driven out from a parking place in front of the building, or something like that . . ."

But then, as Boucher readily acknowledges, "a lot about good quality photography is being in the right place at the right time."

One of the photographs on display -- the porch of the Carson House, in Eureka, Calif. -- prompted one viewer to ask Boucher how he had produced "the smoke" that lingers in the background.

"I'd love to say I did something that exotic, but I didn't. [The coastal fog] was there, and I was just lucky."

There are, however, instances when the intrusions are not serendipitous. Boucher likes to portray the building as it is, "as a document unto itself," but sometimes the 20th century gets between his camera and, for example, an 18th-century adobe church in New Mexico.

"The day that I was there," Boucher recalls, "there wasn't a cloud in the sky. So the picture, the true picture that I made, is deadly. The sky is bare. And what's worse, there are two or three utility lines going right across [the front of the church]. They completely devastate the image of an 18th-century church."

But the picture that hangs in the AIA exhibition has clouds and does not have utility wires. Boucher, through photographic manipulation, added the one and eliminated the other.

"To me, that is perfectly acceptable, because the wires have nothing to do with this building . . . And for exhibit purposes, the picture is much more pleasing to the eye to have those clouds, rather than a bare sky."