Nice aria, shame about the film

Next weekend, why not nip down to the cinema and enjoy... a spot of Wagner. "Cinecasts" have become the coolest way to enjoy opera: increasing enthusiasm for them appears to be sweeping the globe – the sold-out cinemas tell their own story.

The Metropolitan Opera in New York first tested a cinecast five years ago; now, in the era of HD, many more companies are taking up the challenge internationally, and not just in opera. From the Bolshoi Ballet to our own National Theatre, stars of the performing arts are ready to wow us in the comfort of our local multiplex.

Next up is the Met's Die Walküre, the second opera of Wagner's Ring Cycle, which will hit stage and screen on 14 May, directed by Robert Lepage and featuring an extraordinary roster of operatic celebrities including Deborah Voigt as Brünnhilde, Bryn Terfel as Wotan, Jonas Kaufmann as Siegmund and Eva-Maria Westbroek as Sieglinde. At the Met itself you'd fork out around $300 (£180) for a seat. Trot along to the cinecast, though, and you can see it all for a relatively modest £30.

It's a deliciously modern medium. Last month the Met treated the world to Rossini's Le Comte Ory, starring a happy, if exhausted, Juan Diego Florez, whose wife had given birth half an hour before curtain-up. Opera fans in different countries united on Twitter to compare notes, sharing the experience while thousands of miles apart.

Opera and cinema, of course, are by no means strangers. Operatic films have occasionally become classics, notably the 1984 Carmen starring Julia Migenes-Johnson and Placido Domingo, fabulously filmed on location in Andalucia. Opera on film can be a vehicle for starry presences – try Angela Gheorghiu and Roberto Alagna in Tosca (2002), directed by Benoît Jacquot; as for television, last year Verdi's Rigoletto, with Domingo, was broadcast in instalments live at the appropriate times of day from the palaces of Mantua. These projects, though, were one-offs; cinecasts have become a regular feature in cinemas all over the world.

Still, opera and cinema can be uneasy bedfellows. Peculiarly enough, at the same time that live opera went into cinemas, opera companies began to engage big-name film directors to create new productions for stage, not screen. Sometimes it works. The late Anthony Minghella's 2005 production of Madam Butterfly for the Met and ENO was generally adored, won an Olivier Award, and has been revived several times. And when Terry Gilliam's new production of The Damnation of Faust by Berlioz opens at ENO this Friday, everyone will be hoping that the former Monty Python artwork supremo will have enough wit and wisdom to transfer his screen magic to the Coliseum stage.

But other results have been dubious. ENO found success elusive with Abbas Kiarostami's rather static production of Mozart's Cosi fan tutte, and a couple of months ago Mike Figgis's staging there of Donizetti's Lucrezia Borgia was dismissed by one critic as "psychologically moribund, visually dull and dramatically stone dead". Faced with an unfamiliar live and musical medium, superb cinema directors can seem out of their depth: no close-ups, no fascinating camera-angles, and certainly no relying on the dramatic expertise of those in the leading roles, who are not generally selected for their acting.

Opera and cinema make extremely different demands on their directors and raise completely separate sets of audience expectations. The peculiar outcome is that film directors are failing on stage, while specialist opera directors find only second-hand success on screen via the cinecasts.As for the audience, much of the current cinecast craze is down to its novelty. Some of us are trying operas for the first time; sometimes we get hooked.

Hear Jonas Kaufmann or Juan Diego Florez, nearly live, for a reasonable price, from a comfortable cinema armchair rather than an overpriced, under-sized seat that only shows you the stars at the size of pins? The advantage is clear. But – and it's a big but – there's a drawback. This experience of opera may take place in real time, but it is not really "live" because the show is still somewhere that you're not. The truth rams home when the curtain falls and you applaud – only to realise that the performers can't hear you and the rest of the audience is giving you funny looks. The edge is immediately blunted.

Cinecasts are neither truly live performance, nor real cinema. At the moment the emphasis is firmly on showcasing great performing-companies to prove that they can reach a wide audience; the "live on stage" element has been the chief selling-point. But because of the discrepancy between the two media, the artistic result is bound to remain second-best: essentially this is visual radio plus tonsils. Cinema can do much, much more when it tries.

Wim Wenders's Pina, which brings us the late choreographer Pina Bausch's Tanztheater Wuppertal in up-to-the-minute 3D, filmed with exceptional poetry and sensitivity, proves just how effectively stage works can be brought into the cinema. The startling beauty of Pina is likely to win many more new friends for contemporary dance than any number of views of Kaufmann and Voigt's epiglottises will gain for opera. Nor is 3D the answer in itself: the Mariinsky Ballet recently cinecast Giselle in 3D, but the result was widely felt to require considerable fine tuning.

What's needed, above all, is a great enough imagination and the requisite directorial empathy to redesign the performing arts for the big screen and give them the best of both worlds, rather than two thin ends of the wedge. Currently the capabilities of film far outstrip what we see in cinecasts. If opera were tocatch up, the rewards could be stunning.

The filming of opera needs to be exciting, thought-provoking, magical: it should add a new dimension of its own to the experience. Wenders with Pina does precisely that for dance.

And, in an ideal world, filmed opera could become an art form in its own right. Perhaps it will be sooner than we think.

'Die Walküre' from the Metropolitan Opera, New York, will be cinecast on 14 May