“Wagner’s Dream”: a loaded title if ever there was one. Implicit almost throughout Susan Froemke’s documentary film of that name — when it is not explicit — is the notion that Wagner, frustrated with limited 19th-century staging techniques, could have only dreamed of something like the high-tech machine that Robert Lepage has used to stage the “Ring of the Nibelungen” at the Metropolitan Opera.

“When you look at this,” Georges Nicholson, identified as a Wagner historian, said, watching an early stage of the machine’s construction, “you feel like this is finally the ‘Ring’ that Wagner would have wanted all along.”

“We are actually having the vision that Wagner had when he was composing,” Mr. Nicholson added.

“Wagner’s Dream,” directed by Ms. Froemke and edited by Bob Eisenhardt, had its premiere last month in the Tribeca Film Festival. It was shown on Monday evening in theaters around New York and throughout the United States and Canada as a prelude to screenings of the original HD presentations of each of the individual operas: with, that is, James Levine conducting “Rheingold” and “Die Walküre” from the 2010-11 season, and Fabio Luisi the rest from this season. Then, on Saturday, it will be shown at the Brooklyn Academy of Music.

The film, though a bit long at 1 hour 52 minutes (would Wagnerites have it any other way?), is beautifully made. There is — like the production or not — quite a tale to tell, full of its own drama, including serious mishaps in performances as well as in rehearsals, all accounted for here.