Realty Photo Master Corp., a Potomac computer company, thinks it has a marketable product for real estate sales agents: software that combines a picture of Montgomery County houses for sale with detailed information about the homes. In the past year, the company has sold the service to 13 real estate offices.

But the Montgomery County Association of Realtors is not impressed. The group has protested Realty Photo Master's use of information from its multiple listing service of houses for sale, saying the information is protected by copyright law.

Each side now is accusing the other of engaging in unfair trade practices.

"He is taking copyrighted data and merging it with his pictures," association attorney George Ballman said of David Hermrick, founder and president of Realty Photo Master. "He's capitalizing on our product."

But Hermrick said that combining the two sources of data via computer is no different than printing the two items separately and taping them together. Realty Photo Master sells its software only to association members, who automatically have access to the association's listing service, he said.

Hermrick and the firm's chief operating officer, Sharon Rhodes, have accused the association of trying to shut down their operation and create a monopoly for Shannon & Luchs, a local realty firm that has developed its own photo-imaging service for its agents and has five Realtors on the association's 21-member executive board.

"What they're trying to do is resulting in unfair trade practices," Rhodes said. "They're allowing one system to exist without other agents in the county having the opportunity to subscribe to another system."

The conflict erupted May 17 when the county Realtors' board voted to send a letter to Hermrick warning him to stop using the multiple listing service data and to discontinue another service that provides access to association- approved forms through Realty Photo Master software.

After that meeting, Potomac broker Frederick Thoms resigned from the board to protest what he said was an effort by Shannon & Luchs to improve its own situation at the expense of other Realtors. "They weren't serving the public and they weren't serving the membership," Thoms said of the Realtors' board.

William Ellis, Shannon & Luchs's executive vice president, who sits on the association's board, said the board's action had nothing to do with his company.

"Our system is entirely different than theirs," he said. "We do not interface whatsoever with the MLS. We take our own pictures and put in our own data. So why we're being brought into this, heaven only knows."

Realty Photo Master is enlisting the help of its clients in the 13 real estate offices, asking them to contact board members and condemn the association's action.

The two sides opened settlement negotiations last week, but neither seemed ready to retreat from its position.

"We're trying to resolve {it}, but we've been having some problems," Ballman said.