Samuel Loring Morison, a civilian naval intelligence expert and the grandson of noted American historian Samuel Eliot Morison, pleaded not guilty today to charges of leaking classified photos of Soviet shipbuilding operations to a private British military magazine.

Speaking in clipped tones and wearing a baggy cardigan sweater with a paperback book crammed in one pocket, the 40-year-old Morison denied the charges under the U.S. espionage statute during a brief appearance in federal court here before U.S. Magistrate Paul M. Rosenberg.

Later, Morison's attorney, Jacob A. Stein of Washington, told reporters that Morison "is by training and through his forebears . . . an exceptionally patriotic person. . . . This case has nothing to do with espionage."

Rosenberg tentatively set Morison's trial for Dec. 17. Morison remained jailed under $500,000 bond, but will seek release at a pretrial detention hearing Monday before Rosenberg.

Morison's arraignment today marked his first public appearance since shortly after his arrest Oct. 1 by FBI agents at Dulles International Airport as he was about to board a flight to England.

He is charged with unauthorized disclosure of three classified satellite photographs showing a nuclear-powered aircraft carrier under construction in a Soviet shipyard on the Black Sea.

The photos, all classified "secret," appeared in the Aug. 7 issue of Jane's Defence Weekly, a newly established magazine of the London-based Jane's Publishing Company, highly regarded for its authoritative books and periodicals on military hardware.

Material used by Jane's often is based on classified material obtained from a wide range of sources.

Copies of the pictures Morison is accused of leaking subsequently were distributed by wire services and republished in The Washigton Post and other newspapers.

In an FBI affidavit, Morison, a Soviet amphibious ship analyst at the Naval Intelligence Support Center in Suitland, was accused of taking the photographs from the desk of a colleague last July and selling them to Jane's, where he was a $5,000-a-year part-time editor.

"The problem with this case is, when you first hear aboout it, you think of espionage," Stein told reporters. "But it has nothing to do with espionage. He gave nothing to an adversarial foreign government. What he gave was aerial photographs of an aircraft carrier of a foreign government, and I assume the Russians know they are building an aircraft carrier."

The leaked photographs were reported last summer to have caused concern at high levels in the Pentagon, not so much because of the pictures themselves but because of the information-gathering capabilities they demonstrated.

Morison, a studious-looking man with graying hair and a moustache, has worked at the center for eight years and lives by himself in an apartment in Crofton.

His late grandfather, a Pulitzer Prize-winning author, wrote the official history of the U.S. Navy in World War II and was awarded the rank of rear admiral.