Walk into the Opera Loft, one flight up at the Dupont Circle branch of Record & Tape Ltd., and the first thing that strikes your eye is the video screen. The Loft is an unusually well stocked shop specializing in recordings of opera, books about opera, librettos, scores and even posters related to opera. But it is notable above all for a new stock of operas on videotape, introduced on an experimental basis.

In a city that has hundreds of video shops, this is the first one where you can rent or purchase "The Magic Flute," "Adriana Lecouvreur" or "The Marriage of Figaro." It will not be the last. Its stock is still small and the technical quality of its tapes is uneven. But it marks the beginning of something that should grow into a significant branch of the recording industry during the next decade.

On the video screen, the 400-year-old art of opera has at last found its logical recording medium. Even if the picture is sometimes fuzzy and the voices are not always the world's greatest, the experience of video opera gives a kind of satisfaction that has never been available in sound-only recordings.

The supply of video operas is beginning to grow, too. We must wait awhile for the arrival in home-video formats of the new "Bizet's Carmen," with Placido Domingo and Julia Migenes-Johnson, or Franco Zeffirelli's powerful "I Pagliacci," with Domingo and Teresa Stratas. But a large repertoire has already been filmed or videotaped and should be made available if establishments like the Opera Loft can demonstrate that there is a significant market.

Video Arts International, a small company that had specialized in ballet, has begun to issue operas in the Beta and VHS formats. The first two to arrive originally ran in movie houses: Gian Carlo Menotti's 1950 film "The Medium" (VAI.OP.4) and the 1971 "Lucia di Lammermoor" with Anna Moffo in the title role (VAI.OP.1).

"The Medium," in a performance based on Menotti's original Broadway production, differs somewhat from the revised version currently in the Washington Opera's repertoire. The movie is a hair-raising performance, a memorable musical and theatrical experience. In "Lucia," Anna Moffo sings well and looks exactly right. Otherwise, its chief attraction is the atmospheric and beautifully photographed old castle where the dark, brooding tragedy takes place. Both productions take full advantage of the realism and fluidity of action available on film, as compared with the staged productions that have been so far the chief source for video opera. Neither has a sound track that meets today's highest standards -- understandably, considering their age. But for many opera fans a good video element makes a few audio (or even musical) blemishes more tolerable.

Photographed in black-and-white, in a style reminiscent of the stark Realism of post-World War II Italian movies, "The Medium" is the story of a "spiritual" charlatan whose grip on reality is shattered, with tragic consequences, by an incident during one of her se'ances. She feels the touch of an unseen hand, begins to wonder whether all the hocus-pocus is real, and slowly disintegrates. Menotti's well-crafted music rises to an intense climax in the performance, which is conducted by Thomas Schippers.

Maria Powers, who introduced the role on Broadway, is a consummate singing actress, and she is supported by an excellent cast. Anna Maria Alberghetti is theatrically superb as her daughter Monica. Her voice sounds edgy at times, particularly in her first aria, but is generally good, and her style is just right. As the film's director, Menotti shows the same kind of genius that has become familiar in his stage direction for the Washington Opera. He ignores his own quite explicit stage directions repeatedly, and he is quite right -- this performance is tailored to the film medium. The film does not have quite as much impact as a live performance in the Terrace Theater. But it has plenty.

For the video opera enthusiast who has everything, Moffo's "Lucia" ranks second between the two available sight-and-sound recordings. In this case, "everything" must include a LaserDisc playback unit -- the system developed by Pioneer, not to be confused with the CED system introduced and then phased out by RCA. The best video "Lucia" we are likely to see in many years is available only on LaserDisc from Pioneer Artists (PA-84-076). It contains the Metropolitan Opera's televised performance of Nov. 11, 1982, and it is a deluxe production in every way, including the cast, packaging, sets and costumes and recording technology.

The cast is headed by Joan Sutherland, vocally the most spectacular Lucia of this generation, and possibly of the century. It is a pity that the "Lucia" of Maria Callas was not filmed; sound-only recordings emphasize Callas' weaknesses and omit her much of her strength. Without a Callas video for competition, Sutherland's video "Lucia" has no real peers.

One common illusion among opera entrepreneurs is that when you have cast the soprano part you have cast "Lucia." This seems to have been the feeling in making the Moffo "Lucia"; she is surrounded by competent nonentities. Sutherland is supported by the kind of all-star cast that the Met can muster for a gala occasion: Alfredo Kraus, Pablo Elvira and Paul Plishka, with Richard Bonynge conducting. These colleagues help to make the sextet specially memorable. But even in such company, it is still mostly Sutherland's show, and a fine show she makes of it. Her voice remains as rich in tone and almost as agile and accurate as it was a quarter-century ago.

The most amazing discovery, when sight is added to sound, is that Sutherland has developed into quite a good actress -- at least in this role, which she has been singing with distinction for a generation. She does not look like most people's idea of the young woman who is forced into a marriage for dynastic reasons, loses her mind and kills her husband, but her facial expressions and gestures are appropriate, varied and animated.

Moffo looks like Lucia, but doesn't do much with this advantage; her stage image is pretty but static. Her singing (like that of the rest of the cast) is generally reliable but seldom exciting. The Moffo production has the advantages of a movie over a televised stage performance; the performers can move in a real castle with a freedom that is unavailable between walls of painted canvas. And the performance is never interrupted for applause as it is in the Met production, frequently and justifiably. The digital stereo LaserDisc sound is magnificent; the sound on the videotapes is considerably less impressive in general and was occasionally blemished (but only slightly) with flutter in my review copies. In sum, the videotape is a fairly average "Lucia" but the LaserDisc is dazzling.

VAI tapes (Beta or VHS) can be mail-ordered from Video Arts International, Box 153, Ansonia Station, New York, N.Y. 10023. LaserDiscs can be ordered from Pioneer Artists, 200 W. Grand Ave., Montvale, N.J. 07645; or from Starship Audio, 605 Utterback Store Rd., Great Falls, Va. 22066.