AFTER a mere 50 years, soap operas have finally become respectable. Time was when a guilty housewife would flick off the radio or TV if the doorbell rang, not daring to admit she was hooked on "All My Children," "Guiding Light" or "General Hospital."

Soap fans have come out of the closet, due in large part to public confessions by the likes of Carol Burnett, Miss Lillian Carter and Sammy Davis Jr. He even makes occasional appearances on "One Life to Live," saying some of the best actors on TV appear on the soaps. And he's right.

The current 12 shows on the three networks, employing some 400 actors, include the hardest-working toilers in show business. They earn considerably less than their nighttime counterparts, get far less publicity and are generally unreconized execpt by their millions of devoted fans.

Rod Arrants (who plays Travis Tourneur Sentell in "Search for Tommorrow") believes that until last year, "daytime television hadn't gotten a fair shake." It's not quite true: John Berardino, the much-respected actor and long-time Dr. Steve Hardy on "General Hospital" since its beginning in 1963, importuned the Television Academy for special recognition years ago. He succedded, and the daytime shows have had their own Emmy ceremonies since 1973 -- awarded in the daytime, of course.

Soaps are far more realistic than most prime-time shows, and they have unhappy endings as often as happy ones. Author-journalist Alan Gansberg says, "If a continuing drama line is done properly, it hooks the viewers. It is not unlike "The Pickwick Papers,' the timeworn, proven, popular vehicle with cliffhanger aspects. It gives audiences a chance to see problems that are worse than their own, or problems that mirror their own."

Al Rabin, co-executive producer of "Days of Our Lives," is more analytical: "There is a therapeutic value the audience gets from the show. Everyone wants just one person with whom to share an open, honest feeling. On a soap, there are 15 or 16 people who will never lie to the viewer, although they may lie to the other characters.

"I tell our actors to find that moment in the scene where they can tell the audience what they're feeling. If they're sad and about to cry, let the tear go halfway down, and let the audience share the emotion. In nighttime comedy, you get an expression of anger from Archie Bunker or Alice. In daytime, there are emotions the audience can share: anger, pain, hurt or frustration."

There are problems galore: rapes, abortions, murders, divorces, unwanted pregnancies, sterility, impotence, fatal illnesses, long-term-remission illnesses and, quite often, death.

And the action gets heavier in the summer. The Hollywood Reporter of June 10 reported that "the daytime dramas become more competitive in terms of story-lines during the summer months. It has always been assumed that a younger crowd, students on vacation, whatch the shows during June, July and August, and the story-lines will reflect a more youthful look. Summer months are often the time when daytime programs make their move upward in the ratings." For example, producers will schedule a rape scene with a young victim in the summer, and stretch it out over several weeks to appeal to younger audiences.

But if the soaps are violent, they are also instructive. Among their firsts: Charita Bauer as Bert on "Guiding Light" had a Pap smear 18 years ago, because writer Agnes Nixon was aware of its importance in diagnosing cervical cancer. Bauer says, "Hundreds of thousands of women had Pap smears as a result."

When Dorothy Green, as Jennifer on "The Young and the Restless," had a mastectomy on the show, the American Cancer Society was profuse in its thanks to Bill Bell, the show's creator. Thousands of women went to their doctors when they found lumps in their breasts.

Susan Lucci (Erica on "All My Children") had an abortion on that show years before Bea Arthur as "Maude" in prime time deliberated about her abortion. On the same show, Mary Fickett (Ruth) became pregnant in her 40's, with a probability of the child's having Down's Syndrome. She had an amniocentesis test to determine the infant would not be retarded. Millions of Fans

According to recent Nielsen figures, between 20 million and 22 million people are watching soaps in any given hour. Audience flow gradually increases until about 1:30, then reaches a plateau until 2:30 before the show build-up into prime time. Although "General Hospital," "All My Children," "The Young and the Restless" and "One Life to Live" have often been at the top of the charts in recent months, popularity ratings of the various soaps vary almost from week to week. Critic Jon-Michael Reed, perhaps the most knowledgeable journalist in the daytime field, says, "No show is consistently good. It can't be. When the staff of writer changes, the show changes, for better or for worse."

But the audience is solid. The Wall Street Journal reported last month that despite an increase in the number of working women, the number of soap-opera viewers is growing, and soaps are outrunning game shows in popularity. "The game-show format, which draws older viewers, once accounted for half the networks' daytime offerings," the Journal said. "In the coming daytime schedules, however, the networks will devote a total of only two hours to game shows, compared with 6 1/2 hours last year."

Network executives pay considerable attention to daytime ratings, but they don't panic after a show has been on the air three weeks, as does happen in prime time. As a rule, daytime shows are given a year to prove themselves. There have been exceptions: "Lovers and Friends" went off the air in five months. It was rewritten and retitled, "For Richer or Poorer," and died nine months later.

At the other end of the spectrum, "Search for Tomorrow," now in its 29th year, is TV's longest-running daytime or nighttime series. Mary Stuart, as Joanne, an original and very active cast member, has been on TV longer than Lucille Ball! "Ryan's Hope," now in its fourth year, is generally considered the best-written by the Writers Guild and the TV Academy (which awarded it Emmys three consecutive years -- although not this year, when the honor went to "The Guiding Light").

"Ryan's Hope" is perhaps the most realistic of the soaps because it is based on Claire Labine's own Irish-Catholic background. She and Paul Avila Mayer share co-executive producer and head writer credits.

"I drew upon my own roots -- the Catholic experience in America," says Labine. "At the beginning, we did things that seemed new. At first, it startled the audience to see Maeve with her rosary, going to confession. We are not making religious points, but we do keep up with the Vatican actions. Delia wouldn't have gotten her annulment as easily except in Brooklyn -- I use our own diocese there for church annulments," she laughs.

"We deal with birth control and abortions. Siobhan was pregnant in a marriage that wasn't working, and her initial response was to abort, but she couldn't, because from the Catholic point of view, that fetus was a baby. I think the show has real social value in the way our characters explore their problems."

Some experts believe that soaps slotted later in the afternoon are less popular. But a slim, feisty lady has proven it's not so.

When Gloria Monty was named producer on "General Hospital" in January 1978, the series was in "deep trouble," in words of Jacqueline Smith, ABC's vice president in charge of daytime programming. In the recent ratings, "General Hospital" has alternated between No. 1 and No. 2 by a fraction of audience share. Full credit is given Monty, who came from prime-time TV.

How did she work her miracle? "I spent a week watching three weeks of the current shows. They were 1949 style. We must not forget that the same audience watching daytime also watches at night, and this show had't changed in 15 years. We were talking down to the audience!"

Monty moved fast: Elegent new sets were built on a new soundstage at the old Columbia Studios. Actors were given individual dressing rooms for the first time, instead of sharing with fellow actors. Morale zoomed with the ratings.

Monty stepped up the show's pace using editing techniques similar to those used in prime time. She implemented a repertory method of acting, which allowed the cast to improvise when necessary. Instead of starting with Act i and going right through to the end, as has always been the norm in daytime, Monty rescheduled the show to be taped as movies are: If there are six scenes in the living room, they're all completed, and then the cameras move. Her new team of writers, headed by Emmy-winning Pat Falken Smith, now writes 18 to 25 scenes to make the action move faster. She brought in attractive new actors -- Jackie Zeman (Bobbi) and Chris Robinson (Rich) -- and placed more emphasis on Kin Shriner (Scotty), Genie Francis (Laura) and Richard Dean Anderson (Jeff), who were already there. She found herself with a big new audience: Young college students joined the housewifes who'd been her faithful viewers all along.

Monty is delighted that her show came out of the basement. Still more, she cherishes a comment made to her by a visiting Briton at a party:

"I compare 'General Hospital' to Masterpiece Theatre.'"

Although ad rates on daytime TV are approximately half the prime-time cost, soaps are higly profitable, largely because of the wild inequities between daytime and prime-time production costs.

No firm dollar figures are available, but one producer estimates between $90,000 and $200,000 for an hour, depending on production values. Another estimates $250,000 for five hour-long episodes. By contrast, an average hour of prime-time proramming costs about half a million dollars an hour.

Networks count on high returns from daytime programming to balance out the riskier ventures in the evening schedule. As ABC's Smith says, "Daytime has to be a profit center."

And, of course, soap actors aren't getting megabucks like their counterparts in prime time. Salary figures are not generally available, and are subject to speculation. An executive at ABC says NBC's Macdonald Carey on "Days of Our Lives" makes more than anybody else. A spokesperson at NBC says the same thing about ABC's John Berardino on "General Hospital." while someone at CBS thinks Jaime Lynn Bauer on "The Young and the Restless" may make top money. A few years ago, when Time magazine ran a cover on Susan Seaforth Hayes and Bill Hayes, thier income was reportedly $100,000 a year each.

Some actors believe Beverlee McKinsey (Iris on "Another World") is now top lady in the battle of the bucks. She is in an enviable position with a starring role in the new "Texas" series starting tomorrow, a spinoff from her current show.

Other top earners include Denise Alexander (Lesley) on "General Hospital," Mary Fickett (Ruth) on "All My Children," Mary Stuart (Joanne) and Larry Haines (Stu) on "Search for Tomorrow," Charita Bauer ("Guiding Light's Bert), Susan Lucci (Erica on "All My Children") and Eileen Fulton (Lisa on "As the World Turns").

There are ancillary goodies which accrue to actors, including commercials where big money can be made if they get national spots, and personal appearances. Some enterprising promoters realized if they "packaged" a few daytime stars and let the fans see them at shopping malls around the East and Southeast, small fortunes could be made. (Yesterday, Linda Dano and Tony Call, actors on "One Life to Live," were scheduled to appear at the new Fair Oaks shopping center in Virginia.)

Even the actors in minor pars can earn respectable livings if they get a running role, Union scale for a 30-minute show is $267.75 a day, and $367.50 a day for an hour show. Most actors receive over scale. So, assuming an actor works two or three days a week (which is the average) at $500 a day on a 13-week cycle (which is the general guarantee), he has earned between $13,000 and $19,500 in about four months -- less 10 percent to his agent.

And that is why many actors would almost kill for a running on a daytime series.