Les Blank's "Burden of Dreams" is a behind-the-scenes documentary about the troubled production history of "Fitzcarraldo," an ambitious movie project by German director Werner Herzog.

The current version shows marked improvement over the production Blank prepared for a television premiere on PBS earlier this year. The complete "Burden of Dreams" accounts for Herzog's vicissitudes from the beginning, when his first camp in the Peruvian jungle was burned down by hostile Indians in December 1979, through the abandonment of the original production two years later because of illness to Jason Robards. The Robards episode, brushed off quickly in the TV cut, is even illustrated in the expanded "Burden" by a sequence from the abandoned project. This setback also cost Herzog the services of Mick Jagger, who couldn't afford to stick around indefinitely. The clip looks intriguing, not only because of the novelty of Robards and Jagger acting together (they appear at the top of a bell tower while happily sozzled) but also because it suggests a jauntier movie than Herzog probably wound up with after falling back on Klaus Kinski as his leading man.

Without having seen "Fitzcarraldo," it's difficult to assess the value of "Burden of Dreams." Since virtually every movie made is subject to frustrating delays, miscalculations and production problems, one needs the finished film to put the backstage chronicle in proper perspective. In all likelihood the Herzog glimpsed working and pontificating in "Burden" is operating more or less normally -- for him. Given the mysterious, serendipitous aspects of the medium, it's conceivable that the finished film might vindicate his stubborn dedication to a risky, maddening project.

"Fitzcarraldo" is scheduled to open here next Friday, so one hopes "Burden" will not be pulled prematurely. Common sense should dictate simultaneous bookings or even double-billing for these companion pictures.