She posed nude for Playboy in 1983 and again in the film Star 80 that same year, but when Mariel Hemingway undressed for the Civil Wars scene in which her character, divorce attorney Sydney Guilford, models for a photographer-artiste, ''it was pretty nerve-racking,'' she reports. ''They said 'Robe off,' and the crew could see my face turn fuchsia.'' (Like they were looking at her face?)
''Actually,'' says Hemingway, 30, ''I'm pretty shy. Isn't that weird? I won't even wear a bikini on the beach.'' The mother of two admits that's a matter of both modesty and vanity. ''On TV I'm lit well,'' she says, ''and I can choose the angle. I can't edit what you see at the beach.''
In fact, the Civil Wars scene though it raised the stakes a notch in the adult-ifying of prime time ended up revealing less than is often displayed at the beach these days. That even a miniscule percentage of viewers registered their protest took Hemingway by surprise. ''Movies like Basic Instinct are out,'' she notes. ''Demi Moore is naked on magazines. There's Madonna looking like she's doing kiddie porn on a magazine cover. To me, nudity is not news. I've turned on the TV in the middle of the day and seen more on Oprah.''
Hemingway says she and husband Stephen Crisman, 42, a restaurateur (Sam's Cafes in California, Texas, and New York; Sam is his nickname for his wife), found ABC's ''viewer discretion'' advisory unwarranted though it undoubtedly spurred the 1.1 million viewership increase from the previous week for the critically lauded show, which is struggling in the ratings. ''The ironic thing is you can click two channels over to cable and see the world,'' she says. ''The double standard is sort of absurd.''
Provocative roles seem to be Hemingway's specialty: She played Woody Allen's 17-year-old girlfriend in 1979's Manhattan (winning an Oscar nomination), slain Playboy playmate Dorothy Stratten in Star 80, and a bisexual pentathlete in 1982's Personal Best. The Idaho-born actress, who spent a lot of time during her formative years in Europe, finds many of American TV's lingering constraints baffling. ''Maybe I'm naive, but I don't get it,'' she says. ''Sometimes we can say 'God' but we can't say 'Jesus.' I don't get the mentality of that. I still think that people should be more up in arms about the number of people who get shot on TV, not people taking their clothes off.''
Hemingway has even less patience for charges that TV is contributing to a deterioration of the country's morals: ''I seriously doubt I'm going to affect someone's upbringing by having done this scene.'' Her own daughters, Dree, 4, and Langley, 3, are too young to stay up for Civil Wars, but, says Hemingway, ''I would not feel bad about showing this to them.'' Husband Crisman concurs: ''Our kids would think it's pretty cool. She looked great. What's wrong with that?''
Civil Wars' producers, however, should not take this as an open invitation to request regular disrobings to shore up the ratings. ''They would have to find another tall blond to do that,'' Hemingway says. ''I'm not a bimbo who does cheesecake, looking to make headlines.''
''I don't take my clothes off in all my films,'' she adds, with a laugh. ''In my next movie (NBC's Desperate Rescue) I wear lots of turtlenecks, thank you very much!''