The glowing serenity which sets "On Golden Pond" apart as a theater experience also is infiltrating its filming.

Katharine Hepburn and Henry Fonda, together for the first time in their long careers, are leading quiet lives which demand 5 a.m. wake-up and bed-by-9 schedules. Jane Fonda, Henry's daughter, is playing the part of his only child in the film -- and simultaneously playing housewife to her husband, Tom Hayden, and her children, Vanessa, 12, and Troy, 8.

Over them all, from 3,000 miles away, hangs the intensifying Hollywood actors' strike. "On Golden Pond" is exempt -- one of 20-odd U.S. films in production worldwide with special dispensations from the Screen Actors Guild. Backed by Britain's Marble Arch film corporation, Jane Fonda's production company received its go-ahead because this summertime New Hampshire setting is vital to the story of Ernest Thompson's play and because the company has agreed to go along with whatever demands the strike achieves.

Another provisco, according to unit producer Bruce Gilbert, is that there be no publicity of the filming until the strike is settled. The result is that the set (artfully detailed by Steven Grimes) is closed to the media. Only those who agree to withhold stories about the picture until the strike is over are welcome. Though the unit photographer is at work, his pictures will not be released until the strike ends.

This condition, which has nettled the East Coast news media, might have been averted by early notice. But the production's low profile may well benefit the finished film, for all the hundred-odd players, staff and crew -- veterans of hundreds of Hollywood films -- feel that something sspecial is happening here.

There is, indeed, magic on the set as Henry Fonda and Katherine Hepburn explore one another's mastery of their art. With them it is an art, not poses or tricks. Instead of the usual inattention of a seen-everything- been-everywhere crew, there is more than "Quiet Please" as a scene begins and climaxes. There is awe in this silence.

Fonda, at 75, is playing crusty, unpredictable Norman Thayer about to celebrate his 80th birthday, Hepburn, at 70, is the 69-year-old Ethel Thayer,whose teasing of her husband masks the understanding solicitude she has brought him during their long marriage. They are spending their 48th summer at their lakeside cottage, her own summer home as a child. She has sent him off to pick berries from the long-familiar patch down the road and now he is back with an empty pail. Why? Thayer confesses: "I got lost."

In fonda's facer there is despair inHepburn's the realization that this ever-independent man of hers is crumbling. Two lifetimes are crystalized in an instant.

The scene ends, the cameras stop and in the hush a score of men brush moisture from their eyes. "Whew" murmurs one of them.

Later, Hepburn confides: "working with Henry brings tears to my eyes. He is so sensitive, so giving an actor.I've always admired him, of course, but working with him for the first time is a marvel."

Later still, Fonda says forthrightly: "What a joy to be acting with Katharine. She can play all the levels of a scene, and always is able to do something so fresh with a slight gestureor a look."

Later yet, I relay to each what the other has said on the hunch that they wouldn't have said it to each other. Hepburn's superbly mobile face brightens: "Oh I'm so glad. I didn't know." Fonda's eyes light up: Golly, did she really say that?"

To a reviewer who had never met her, Katherine Hepburn had always suggested something of the grandeur of Tzu Hsi, the 19th-century dowager empress of China. Those around her have seemed distinctly protective, and in public she has seemed as elusive as royalty and just as likely to pop up anywhere -- in box-offices, for instance, where she often pays for a single seat.The Hepburn image is awesome. But here everyone calls her "katharine." Others are "Mr. Fonda," "Miss Fonda," or "mr. Lanteau."

She teases a lighting man by boxing with him. She leans on an overalled grip. She puts her arm around the neck of a soundman while talking to him. She is astonishingly, delightfully tactile, always reaching out. She seems to treat others on the set as extensionsof herself, a camaraderie of equals.

"filmmaking is painfully slow," she says, "forever waiting around for setup to be just right, the light from the sky, the sounds of motorboats on the lake. tBut I lovee it! I'm a morning person, always up by 5:30 and rarin' to go. You adjust. The short takes may seem difficult to pick up but you put your mind to it and you know where you are.

"Not like the theater at all. Now that's hard, hard, hard work, those three compressed hours. Night after night, all those years, I sit in my dressing room literally frozen with terror.

"Why am I doing this, I think to myself, why can't I ever get used to it?

But I never can and I'm always terrified. Once it starts, of course, you get going and there's no time to think of anything else but what you must do."

One "price you pay" for being a star, she says "is the constant awareness of how many others are depending on you. It haunts you. Me, anyway. I'm a New Englander. You can't be sick. If you break an arm or a leg you wear a cast and go on anyway as I've done. You've always got to be up because if you go down, everyone else does too."

Talk of touring leads obliquely to the subject of airplanes. Hepburn goes into a knowledgable discussion of how aircraft work. She is told that author Thompson has just taken off for a quick trip to New Ork; "I told him all the routes to take" and she reels them off. "He was going to take a different one." And she reels off Thompson's projected route. "my way would have saved him at least two hours."

She discusses bouillabaisse, which her hairdresser-chef, Ray Gow, prepared in honor of Fonda, "though it's not a favorite of mine." She can rattle off exactly what goes into bouillabaisse, how and when. There is, you conclude, nothing in this world which does'nt interest this women and which she hasn't inquired into and remembered.

Her face is remarkably unlined, still freckled, and her eyes more blue than they seem from a distance. She is far smaller, slilghter, than you expected and though she presently is suffering from a painful right shoulder, her movements show no sign of it.

"It was the last set of a three-day spate of tennis" in Connecticut, she says, that did the damage. "I racketed my shoulder completely out of joint and it was beginning to get a bit better up here when I walked right into a glass door. Now, it's in constant pain. I can't move my fingers, which I much want to do for the piano in West Side Walltz' (playwright Thompson next play). I can barelly raise my arm -- see? But what can you do?You just go on and make the best of it."

Location work never is easy and with so many outdoor scenes affected by sun, clouds and water, the pace is necessarily slow. Though only a handful of people are central to the story, it takes a staff of over 100 to keep things rolling. That includes the crew of "Michaelson Food Services Inc.," which has rolled all the way from Sun Valley, Calif., to rural New Hampshire. Their lunch-hour offerings feature three-course meals such as lobster, crab, filet mignon or trout almondine.

All the staff are under the artistic conrol of director Mark Rydell . Even-tempered and usually smiling, Rydell is a Westernized Bronxite who says, "Why shouldn't I be smiling? Look at the cast and crew I'm working with - the best,the absolute best. If I blow this one, it'll be my own fault.

"Once Jane Fonda, her own production boss, had three leads cast -- herself, her father and Katharine -- I was chosen to direct.It must have seemed very iffy to Katharine. Soon as she heard I'd directed "The Rose,' she scuttled off to see it and that must have given her an awful shock. From Bette Midler to Hepburn?.

"then she had !The Rievers' screened for her and she could see why I'd been picked. "That's a fine picture, she said to me, 'A fine picture. Had I seen only "The Rose," I would have thought Jane had gone out of her mind to choose you for so quiet, mellow a film as this.'

"So, we get along very well and enjoy a mutual respect. Of course we're all in awe of her, but she listens to me. I listen to her. She's a total professional. So are the Fondas and this entire crew."

"Jane was determined to do a picture with her father," Rydell says, "though essentially her role is relatively subordinate to her usual casting."

Jane's role of daughter Chelsea doesn't enter the shooting schedule until later but she's actively preparing for a film assignment she's never had: a back-flip dive. She practices this several hours a day as well as holding those exercise classes she's famous for in Los Angeles.

Joining her daily are her stepmother -- Henry's outgoing wife, Shirlee, only a few years older than Jane -- and actress Patricia McCormick, author Thompson's longtime companion, with her two children. Add to the youth list actor Douglas McKeon, who's playing the lad who retrieves Thayer's wandering attention.

McKeon is shooting his scenes as early as possible because he must be back when the California public schools open. A sunny-faced towhead, he's been acting for nine of his 14 years and has his scenes down with uncanny concetration. He's all prepared for that traditional first assignment of any fall term: "How I Spent My Summer Vacation."

One morning, Henry Fonda stretches his long, blue-jeaned legs from his canvas armchair and muses:

"Think of how lucky I've been these last few years. At a time of life when there aren't many leading parts for an old duffer like me, I've had four beauts. Clarence Darrow in the one-man 'Darrow.' Justice Daniel Snow in "First Monday in October.' Col. Kinkaid in "The Oldest Living Graduate,' which we just finished on stage in Los Angeles after doing in from Texas on TV. And here's Norman Thayer. Beautiful parts, all of them.

"Didja know I might have done George in Albee's 'Who's Afraid of Virginia Wolf?' But the agent never sent it to me. Didn't think I'd like it. I hit the roof after I learned that and wrote Albee to send me his next one. He did, 'Seascape.' I phoned him I'd love to do it. In the the same mail was another script. 'Darrow.' What a devil's choice! I thought it over and called Albee back to renege. Awful thing to do, wasn't it? But I couldn't have missed 'Darrow.'

"And now, working with Jane, or about to.She's the mind behind all this casting because we've always wanted to act together but never could find the play or the picture. The strike thing's been awful for her and while she's met all the requirements, it does rankle. Of course the part isn't anything like the Oscar-winners she's had. D'ya realize she's won two Oscars and I've never won any? Here we have some finely written scenes together.

"It's a novel family outing. She and Tom and the children. They live in the next largest house. Katharine has the big one. She so charmed the people who earlier had taken a two-week, mid-August lease, that they just decided to do something else so that she can stay put. Katharine was going to take Shirlee's and my house and we were going to move down to Jane's and where Jane was going to go I'm darned it I know.

"But that's Katharine's charm for you. You know the people next door, the Burrells, had no idea that a film company was moving in for the summer a hundred feet from their house with all this equipment and bustle. I'm sure they weren't pleased exactly. Katharine decided that someone had to play diplomat so she did it. She went over and introduced herself: 'I'm Katharine Hepburn. We're making a movie next door and I hope we're not ruining your summer.' Can't you just hear her say that?

"Katharine told them to come over and watch anytime they liked and of course that changed the atmosphere completely. Now they're interested and, I hope, rather enjoying it. Someone should have done it earlier, but trust Katharine. She thought of it and did it."

Fonda says his "proudest memory" is of last winter's Life Achievement Award from the American Film Institute, presented at the Kennedy Center."The presidential Box, the White House, all that. Shirlee and I have been married 18 years now but that certainly was a highlight for us.

"She's my real keeper. Nobody gets to me except through Shirlee. I'm the beekeeper, the only one in Bel Air, I guess. I enjoy farming at our place. Must be the most expensive darned farming land in the whole earth. Think of that, me from Nebraska, Bel Air farmer. Shirlee's mother's looking after our place while we're gone and I kid her that if anything dies, it'll be her hide.

"Katharine was talking about those nightly three hours you get during a play's run. It is tough but I've found a way to wind down with my painting. It's fine, concentrated work and you can't think of anything else. Another way I found to wind down, if you can imagine it, is embroidering. Imagine, this gawky guy embrodiering so he can go to sleep."

"Lunch Break," calls Rydell.

Fonda is quickly out of his seat. He'll be first in the chow line right up there with the grips. Mister Roberts still hanging out with his crew.

"Didja ever see anyone like him?" asks one of them. "Always lining up with the rest of us when he could be waited on. I guess that's why we call him Mister Fonda."

Ernest Thompson, whom I first saw act a dozen years ago at American University when he was 19, is used to location filming as an actor, but this is his first time out as a screenwriter, and director Rydell seems glad to have him on tap.

"The weather controls what we shoot," explains Thompson, "and when we're falling behind, as we have been doing, that means we have to think of the budget. So Mark asks me to come up with new ways to cut out scenes without losing the salient points. That's why I'm sometimes turning 20 pages of script into six. Tough, but it's got to be done."

Another reason Thompson is here is that Hepburn is to star in his next play. "West Side Waltz," a piece about three women and a few other people living in old apartments near New York's Riverside Drive.

Before "West Side" rehearsals start, however, Thompson will be off for a Los Angeles production of his first script, three one-act plays titled "Answers."

How does he get his work done?

"See that canoe?" he says. "I paddle out in the middle of the lake and it takes 45 minutes for anyone to find me.