What would have been the end of a routine photographic assignment for William S. Weems, 44, turned into a tragedy yesterday that took the lives of Weems' friend, 45-year-old Robert Joy, who went along "as a lark," and a 24-year-old realty company staff member standing in for her boss.

At the last minute yesterday morning, Victoria Hinckley of Alexandria replaced her boss from Sumner Realty on the photo flight, said Jeanette McManus, a former neighbor from Hinckley's home town, Rockville.

"Torry loved to do anything. I'm sure she went in that helicopter because it was new and she had never been in one," said Mary Jane Walton, also of Rockville, who said she has known the Hinckleys for 30 years.

Joy, a former Peace Corps volunteer and official turned toymaker who ran an innovative Georgetown toy store called the Red Balloon, went along on the helicopter ride "just as a lark," said Shelley Yerman, Weems' business manager and neighbor.

"He always wanted to see what it would be like to go up in a helicopter with Bill on one of his shoots," Yerman said.

Weems, a noted free-lance photographer who worked for the National Geographic magazine and had published several pictorial books, had waited several days to take the last photographs for a promotional brochure for Sumner Realty, friends and colleagues said.

"He had done four or five days of shoots over a three-week period," said Gerry Willse, senior vice president of Barton Gillet, a marketing firm that had hired Weems for Sumner Realty. "He was waiting for a clear day."

The award-winning photographer, who had done major pictorial pieces on Georgia, North Carolina and Hungary for the National Geographic, amassed a large collection of aerial photographs of Washington.

"Helicopters are one of the highest risks a photographer can take," said Bill Garrett, photo editor of the Geographic. "We've had terrible luck with them." Garrett, who survived a similar accident, said Weems was the second Geographic photographer killed recently in a helicopter crash.

Weems, a native of Atlanta, was a legislative assistant to Sen. Daniel K. Inouye (D-Hawaii) before becoming a full-time free-lancer in 1975.

A pictorial, "Georgia: the Home Place," garnered Weems two New York art directors club awards in 1979. Weems' fourth book on the South is to be released next week.

"Everything was just starting to happen to him, professionally and personally," said Steve Uzzell, a longtime friend and colleague. "It's just so grossly unfair."

Weems is survived by his wife, Prisca, a Hungarian refugee Weems met in 1982 while on assignment in that country for the National Geographic, and two children.

Born in Boston and a 1964 graduate of Boston University, Joy was a Peace Corps volunteer in Venezuela from 1964 to 1966, and served as a program evaluator for the corps until starting the toy store in 1972. He returned to school at Ohio University in 1967, receiving a master's degree in photojournalism that became a common bond between Joy and his Mount Pleasant neighbor, Weems. Until their recent move to a house in the Palisades section of Northwest, the Joys lived for years only two doors down from Weems.

Joy, a skilled woodworker, made many of the toys sold at the Red Balloon. In 1975, the store moved from 31st and M streets NW to its present location at 1073 Wisconsin Ave. NW. It was closed yesterday.

Joy is survived by his wife Linda and two daughters, Tatum, 12, and Brenna, 8.

Hinckley, an administrative assistant for Sumner Realty in the District, was described by former neighbors in Rockville as someone who liked to try new things.

"She loved to travel. She was a vibrant person," McManus said.

A 1985 graduate of Mary Baldwin College in Staunton, Va., Hinckley majored in psychology and childhood education. Staff writer Elizabeth Lazarus contributed to this report.