IT WAS A GRIM display of photographs you don't ususally see on the mall at Tysons Corner early on a Tuesday morning, where people who have time and money on their hands go strolling past the stores, credit cards at the ready, with visions of spring wardrobes and redecorated living rooms clicking through their minds.

Poverty doesn't belong in this fantasy land of suburban plenty, and yet there it was: a bulletin board covered with stark, colored photograhs of housing that serves as homes for the poor people of Fairfax County, homes with no heat, no indoor plumbing, dilapidated wooden shacks such as the one where a woman raised eight children alone, spending what income she had on her children with nothing left over to maintain the house.

This is the hidden part of the housing problem in Fairfax County where the median price of housing in 1977 was $78,220 for a single-family home, and where the middle-class is so busy complaining about its housing costs and trying to keep the mortgage check from bouncing that it doesn't have time anymore to worry about poor people's housing problems.

But there are exceptions. There are people such as Charles Davis, a member of Grace Methodist Church in Manassas, who works in the FBI photo lab and volunteered his time to take pictures that would tell the story of poor people's housing in Fairfax. And there are people such as Earl Masincup, the retired assistant director of civilian personnel for the Army, who is now president of the Wesley Housing Department Corporation. WHDC is a Methodist Church organization that emerged in the mid-1970s, a time when Fairfax County had repeatedly rejected efforts to build low-and moderate-income housing.

WHDC is a volunteer organization created in the belief that prevailing attitudes in the county toward low-and moderate-income housing simply weren't right. The bulletin board the WHDC displayed at the third annual volunteer fair at Tysons Corner yesterday showed the housing conditions that exist in Fairfax, but it also showed that something could be done about them. Next to pictures of abandoned housing and shabby trailer parks were photographs of Strawbridge Square, a 128-unit housing project that will open in late May in southern Fairfax. Strawbridge Square is the creation of the WHDC, and it is a monument to the conviction of a group of Methodist volunteers that decent housing is a basic human right.

But it is also a monument to the fact that there are still those who care deeply about others in an age in which we are turning away from social concerns.

Earl Masincup went to his first WHDC meeting four years ago at the request of his minister. "The first meeting I went to, this outfit didn't have more than $200 or $300 in assets. And now, within a period of a little over three years, we're about to move residents into a project with a budget of over $4.5 million."

"It wasn't popular," says Masincup of low-incoming housing advocacy, "but recognition of the need was emerging." Strawbridge Square is located in the Lincolnia section of Fairfax on 21 acres of land donated by the Edward Lynch family. It is an attractive mixture of contemporary-style town houses ranging up to four bedrooms in size and garden apartments with one and two bedrooms. It will be rented to low-and moderate-income families who will pay no more than 25 percent of their incomes for housing. The properties will rent at their fair market value with the difference being picked up by the federal government.

The project has not been without opposition, says Masincup, "but we've found that lessening. We try to share with all interested parties everything we do before we do it. We try not to let any surprises occur."

"This is not public housing," he says. "Every bit of the building, financing and income is done on a 100 percent business basis. The government assistance is to the residents. The whole project has to be financed and operated on a strictly business basis."

There were times, he says, when Strawbridge Square looked like "a dead project," times when WHDC could not find land or when it ran into insurmountable citizen opposition and government red tape in securing financing and when the zoning came through and construction was about to begin and when they ran into an old, unknown landfill that had escaped detection during test borings. It cost $130,000 and took 800 truckloads to cart away the waste and replace it with good soil.

Nine of the 21 acres in the Strawbridge Square development have been returned to the county for park use. The development includes a community room where youngsters from the Lincolnia section of Fairfax can congregate, a room that will be manned by volunteers and maintained through grants from the Methodist churches and businesses in the county.

Strawbridge Square is not the only project of the WHDC, but it is the largest, and it is the first to be completed, and it is a project that is the result of incalculabe numbers of man-hours from hundreds of church volunteers. With 128 units, it isn't much, in a county whose officials estimate there are 26,000 families who need housing assistance. Yet it is a project that reaffirms the value of individuals and the value of their time in an age in which we tend to ignore that tradition and turn to governments for grand solutions.

Ask Earl Masincup why he got involved, what's in it for him, and it's refreshing to hear him hesitate, not give a fast answer. He talks about the satisfaction of knowing he has done something to fill a real need, and then he tells the story: "I'll never forget the feeling I had when we brought some things to a family that was down and out one Christmas. Here was my family, going to have a real good time at Christmas, and here was this family that was down and out. The father had been a truck driver who'd had a real serious accident. I guess it gets down to an awareness that there but for the grace of God, go I."