Dir: Bertrand Tavernier. France. 2001. 170mins.

An ambitious, enormously detailed portrait of a complex and (internationally, at least) little known footnote of World War II, Safe Conduct observes the film-makers working at the Continental, a German studio set up in Paris to produce French movies under the Occupation. Bertrand Tavernier's contention is that much of the resulting work was far from bland pro-Nazi propaganda or frothy escapism and that the French artists at Continental were driven by a range of motives. Sometimes these were craven, complicit or self-serving. In other cases they were irreproachably honourable. With humour and subtlety, the film creates a vision of an era when there were few clear-cut heroes and villains: even Doctor Greven (Christian Berkel), the enigmatic, Francophile Nazi in charge of the operation who sacrilegiously uses the bust of Hitler in his office as a coat rack. The film's commercial downsides are an exceptional running time, its lack of star box-office names, a superabundance of characters and a likely lack of familiarity outside France ( where it has taken taken $1.6m from 187 screens after three weeks) with the cavalcade of films and artists it commemorates. Still, canny specialist distributors should secure this a safe passage towards discerning upscale audiences.

In this vast fresco (115 speaking roles), two men, based on real-life individuals who the director knew personally, stand out from the crowd. Played by Denis Podalydes, the scriptwriter Jean Aurenche (who collaborated with Tavernier in the 1970s on The Clockmaker Of Saint Paul and The Judge And The Assassin), is an moody intellectual firebrand with a fierce sense of independence who lives out of a suitcase helped by a string of indulgent mistresses. Jean Devaivre (Jacques Gamblin), an assistant director, is a stable and dedicated family man whose principles lead him into audacious, sometimes reckless acts. He joins the Continental for pragmatic reasons, regarding it as an excellent camouflage for his work in the Resistance.

In France, the film's release was overshadowed by a robust and very public dispute between Tavernier and Devaivre, now 89, who accused the director of misrepresenting his character and exploiting his experiences (the film states that it is "freely inspired" by his and Aurenche's memories). However, it seems puzzling why Devaivre should take issue with his portrayal as a profoundly decent and heroic man. Abroad, questions of strict fidelity to the facts are unlikely to be relevant.

The central characters' contrasting personalities are introduced in a long opening sequence in which a bombing raid interrupts Aurenche's assignation with his latest mistress, while Devaivre and his wife (Marie Desgranges) are concerned for the safety of their small son. Throughout, the two men's paths barely cross - as was the case in life - and this, combined with the plethora of characters and incidents, gives the film a baggy, unstructured quality.

But in other ways this is a strength, since it enables Tavernier to avoid pat moralising and easy conclusions in his complex exploration of personal integrity. The film is packed with sharp incidental observations: presented with a romantic bouquet, an actress is less impressed by the red roses than by the leg of lamb nestling in their midst. Roving through the chaotic and bustling world of Continental, Alain Chouquart's brilliantly fluid camerawork adds to the film's documentary feel.

The most conventional sequence in dramatic terms is a long, fourth-act comic set-piece in which Devaive, on impulse, steals a Nazi file and is sent on a long chase through France, which ends with him being airlifted by British Intelligence and plied with questions and endless mugs of tea by sceptical officers. Although suspenseful and funny, the interlude feels like a detour from Tavernier's central theme: how creating art under extreme duress can be both a compromise and a means of asserting one's personal freedom.

It would also have been welcome to have a stronger sense of how the dissidents were able to buck the system and to see more of Continental's actual productions. These are glimpsed only in a handful of tantalisingly brief excerpts, although there is one heart-stopping moment when Devaive's brother-in-law, who died in a German camp, comes back to life again for a fleeting moment in a slow-motion clip as an extra in one of the films.

Prod co: Les Films Alain Sarde
Int'l sales: StudioCanal
Prods: Alain Sarde, Frederic Bourboulon
Scr: Tavernier, Jean Cosmos, based on the memoirs of Jean Aurenche and Jean Devaivre
Cinematography: Alain Choquart
Prod des: Emilie Ghigo
Ed: Sophie Brunet
Music: Antoine Duhamel
Main cast: Jacques Gamblin, Denis Podalydes, Charlotte Kady, Marie Desgranges, Maria Pitarresi