For the 72-person press corps risking sunburn, waterlog and tennis elbow to bring you President Reagan's Memorial Day weekend, the drama has been a double feature.

The daily serial has been television networks' maneuvering to photograph Reagan on his secluded ranch from a neighboring mountaintop in what has become called "The Battle of the Lenses."

It has shared the spotlight with an exclusive newspaper report dubbed "The Slaughter of the Field Mice."

Since Reagan refused to grant the press any "photo opportunities" during the weekend, the networks set out to get pictures as best they could. Fresh pictures are to television news what fresh meat is to carnivores -- a necessity.

By a dirt road best climbed in a four-wheel-drive vehicle, cameramen reached the top of one of the Santa Ynez mountains, from which they can train long lenses on the Reagan's small adobe ranch house, and watch the moving specks that are the president, Nancy Reagan, presidential aides and Secret Service agents.

NBC won the initial round by finding the mountaintop first. CBS rallied by dragging a huge camera last used to scan the sky and photograph the return from space of the shuttle Columbia up the dirt road. Cable News Network also found the mountaintop, but, as of this morning, ABC's position in the battle of the lenses was unclear.

One thing was certain. The television viewers had to take it on faith that one of the moving specks was Reagan.

George Skelton, White House correspondent of the Los Angeles Times, scooped his colleagues on the field mice.

He reported that, while the small, furry creatures love the Reagan's house, Nancy Reagan hates field mice. To ease his wife's concern and protect his hearth, Reagan had set out traps to catch the invaders, Skelton reported.

Other reporters bombarded deputy press secretary Larry Speakes with field mice questions. They asked for a mouse body count or other details of the grim struggle said to be going on in secret in the mountains 20 miles north of Santa Barbara.

Speakes would not confirm the field mice invasion. No body count was announced. If the president was setting traps it remained a clandestine operation.

The reliability of the field mice report was thrown somewht into question by another element of the same story.

Depty White House chief of staff Michael K. Deaver, one of Reagan's cloest associates, was misquoted as saying that the president's favority vacation pursuits -- horseback riding, cutting brush and clearing trails -- would take 25 years off his life. Deaver, of course, had said such relaxed activity would add years to the president's life.

Speakes gave his daily briefing this morning to a press corps dressed in an assortment of shorts, sport shirts and slacks and accompanied by an assortment of spouses and children. Speakes, in a checked western shirt and jeans, came alone.

Questions and answers droned on as predictably as they do at the White House. On the missions of presidential envoy Phillip Habib to the Middle East, Speakes said: "We're watching developments closely." Other familiar words and phrases were voiced: "Hopeful," "dangerous situation," "no comment."

Reagan, Speakes reported, was riding a different horse for the third day while Mrs. Reagan remained faithful to her horse, No Strings. No explanation was given why the president chose Gwalianko today after riding Will's Fancy Sunday and Little Man Saturday.

"As you might guess," Speakes said, "the president plans to get in some brush clearing and wood cutting in the afternoon."

Speakes also announced two presidential nominations: Jerry L. Jordan to be a member of the Council of Economic Advisers and James Hackett to be associate director of the International Communication Agency.

Christof Blackman Putzel, the son of two Associated Press reporters, grew restless and gave voice to some annoyance. At 19 months, he ws the youngest person listening to Speakes." He drank peacefully from a blue bottle and played with one of his blue sneakers during the conclusion of the daily briefing.