A Cincinnati judge refused yesterday to dismiss obscenity charges against a gallery that showed an exhibit of Robert Mapplethorpe photographs, and scheduled a trial for Sept. 22.

"I'm not surprised," said lawyer Louis Sirkin, who represents the Contemporary Arts Center and its director, Dennis Barrie. "We suffer our disappointment and go on to the next round."

Senior Assistant City Prosecutor Frank Prouty declined to comment.

Judge David Albanese noted that the case is apparently the first obscenity prosecution of an art museum or gallery in U.S. history, but he observed that the not-for-profit arts center is "more aptly defined as a gallery" and is not technically a museum under state law. Arts center officials showed the Mapplethorpe work, which includes homoerotic and sadomasochistic images, even though they knew "that a confrontation was inevitable," he said in his ruling.

Albanese rejected several procedural arguments advanced by the arts center, including the contention that prosecutors unfairly focused on the center when examples of Mapplethorpe's work could be seen in libraries and bookstores in the area. "It is well documented that a conscious exercise of some selectivity in enforcing the law does not in itself violate the U.S. Constitution," Albanese held.

The judge will hold an Aug. 20 hearing on whether the jury may focus only on seven photographs identified in the indictments or whether the entire exhibit must be considered. The Supreme Court has ruled that works must be considered "as a whole" when obscenity determinations are made.

Cincinnati prosecutors went to a grand jury within hours after the arts center opened the Mapplethorpe exhibit on April 7 and won an indictment against Barrie and the center on two misdemeanor charges each. Police then cleared the crowded arts center to videotape evidence, but a federal judge issued an order forbidding local authorities to interfere with the exhibit. The show remained open as scheduled through May 26.

Mapplethorpe's works sparked the ongoing controversy over freedom of expression and federal funding of the arts after Washington's Corcoran Gallery canceled the exhibit last summer.