Fleshing out a legend isn't easy --

especially when the legend is photographer Diane Arbus, who has been wrapped in mystery by her family and flattened into myth by her fans since her suicide in 1971.

But two current shows -- one at the Corcoran, another at Marie Martin Gallery -- offer some real insight into the working life of this extraordinary artist.

Over the past year, Arbus (who would now be 62) has begun to come into focus thanks to two fine books: a fact-filled biography by Patricia Bosworth published last year (and just out in paperback) and, most recently, "Diane Arbus: Magazine Work, 1960-1971," an Aperture book (also in paperback) edited by daughter Doon Arbus and Diane's late, great friend, artist and art director Marvin Israel. It is this latter book that was the impetus for and core of the exhibition of the same title now at the Corcoran.

With 79 photographic prints and several photo-layouts from the original magazines, it is a twofold revelation. For it brings to light a major body of Arbus' photographic oeuvre, most of which has not been seen since its original publication in Esquire, Harper's Bazaar, the Sunday Times Magazine (London) and other mass-media publications for which she free-lanced until the end of her life.

But the show also reveals another startling fact: Arbus could write, and often published word portraits of her subjects -- including Mae West, Tokyo Rose and the residents of a nudist colony in New Jersey -- that are as intimate, startling and revealing as her photographs. Any reader of her captions and text is bound to wonder why her devoted editors didn't make greater use of her writing talent.

Though often perceived as a weird, fringy denizen of the demi-monde of freaks, transvestites and nudists whom she examined with such intensity, this show presents Arbus as a pragmatic, hard-working, idea-hustling free-lance photographer who got magazine assignments by proposing off-beat story ideas and then delivering the goods. At $150 a page it wasn't much of a living ($5,000 during her best year), but it kept her going, as did two Guggenheim grants. Magazines also brought exposure and support during a period when her style and technique were coming to full maturity, something that can be clearly observed in this show.

Some of the magazine assignments produced classics, such as "Affinities," paired portraits of good friends, including the baby-faced Gish sisters huddled in fur coats in snowy Central Park. At another end of the emotional spectrum are the haunting photographs for a story titled "Two American Families," one posed with their retarded child, the other sunbathing in their yard in Westchester, New York, of which, wrote Arbus, "the parents seem to be dreaming the child and the child seems to be inventing them."

There are fashion pictures too, an endearing one of her saucer-eyed daughter Amy wearing beret and velveteen for "Bill Blass Designs for Little Ones," and a nothing-short-of-pathetic one of an antiquated fashion luminary titled "Fashion Independent," both shot for Harper's Bazaar. Arbus' sympathies seem to intensify as she descends the social ladder, and stripper Blaze Starr seems a near-tragic figure as she poses first in her pasties and worn body and then in stretch pants at home. If there is any obscenity observed in Arbus' portraits of Starr, it is the decor of her suburban living room.

On the subject of worn bodies, another unforgettable portrait is that of Brenda Diana Duff Frazier, 28 years after she appeared on the cover of Life magazine as the most famous debutante of the year. Wearing heavy makeup and smoking in bed, not far from her pill supply, she was photographed for a 1966 Esquire story ironically titled "The Girl of the Year."

The show (and the book) distort Arbus' career a bit by suggesting that her magazine work began only in 1960, when in fact she had 13 solid years of experience in a fashion photography partnership with her husband, Allan Arbus (now an actor), before striking out in the late '50s to pursue her own vision.

It also destroys some myths: The shot of a corpse taken in the city morgue, often used to illustrate Arbus' "morbid" twist of mind, is revealed here to have been suggested by an editor. And it makes clear how much Arbus treasured the access that press credentials gave her to the people and places she wanted to photograph. She made her assignments play to her own goals, and the fact that most of these photographs emerge as distinctly "Arbus" images is a tribute to the power of her vision, even while on commercial assignment.

The vintage prints in the show were lent from the Esquire Collection, now part of the collection of the Spencer Museum, University of Kansas, Lawrence, which organized this traveling show. It also includes several contemporary prints by Neil Selkirk, Arbus' printer, on loan from the Arbus estate. Arbus' Influences

Marie Martin Gallery in Georgetown (3243 P St. NW) is showing "Diane Arbus: Influences," a provocative little show of vintage prints by the photographers -- all of them great -- who influenced Arbus, including her teacher Lisette Model, her contemporaries Weegee and Robert Frank, and also Walker Evans, whom she deeply revered, and predecessors in straight-on photography, August Sander and Erich Salomon.

Those who know Arbus' work will pick up the reverberations clearly intended by organizer Harry Lunn, now a private dealer in New York, who handles part of the Arbus estate. But of all the masters in this show, it is Louis Faurer who is most powerfully represented, and whose images of twins seem to have the most profound affinities with her work, and doubtless influenced her.

Faurer, who still lives and works in New York, has never had the recognition he deserves, and if there are hidden treasures in the photography market today, they may well include his images. That Arbus admired his work was a fact considered sufficiently important by Faurer to take note of it on the back of his photograph of "Eddy" -- a cross-eyed retarded man holding a flower -- making it doubly rare and important.

Also on view, in the back gallery, are some rare vintage Arbus prints, including the famed exasperated boy with toy hand grenade, the crying baby titled "Loser in the Diaper Derby," and the elderly nudist couple in their living room.

There is a touching and revealing item that Lunn owns, but does not have on view, and it may be possible to see it upon request. It is a small postcard Arbus sent to Mr. and Mrs. Walker Evans after her first show opened at the Museum of Modern Art in 1967. It reads: "Dear Isabel and Walker, I knew you couldn't get to the opening but please do see it soon and if there is a print you want tell me so I can give it to you."

The Corcoran show will continue through Aug. 25, the show at Marie Martin through Aug. 3.