In addition to the words of the artist herself, “Marina Abramovic the Artist Is Present” collects testimony from art historians, dealers and curators, notably Klaus Biesenbach, the enthusiastic impresario of the MoMA show, who likens working with Ms. Abramovic to a love affair. And an actual love story is embedded within the film’s summary of her life. In the 1970s and ’80s she and the German performance artist Frank Uwe Laysiepen, known as Ulay, were lovers and artistic collaborators, a partnership that is narrated by both of them. Captured in occasionally haunting images, it suggests a great unwritten novel of creative passion and romantic disillusionment.

The wry, gray-bearded Ulay is the most vivid supporting player in “The Artist Is Present,” and his reunion with Ms. Abramovic is touching and sweet. But the emotional power and, finally, the aesthetic interest of the film reside in its attention to the work that provides its title and its reason for being. The daily spectacle of Ms. Abramovic in her chair at MoMA is brought back in all its strangeness and excitement, and you also catch a glimpse of the logistical challenges involved in staging something at once so simple and so radical. (The patience and professionalism of the museum’s security guards are one of the film’s unstated themes.)

Mr. Akers has performed a valuable service for both the artist and the public in presenting a persuasive answer to the question that still plagues art that creates events and experiences rather than paintings and sculptures: Is it really art at all? Ms. Abramovic offers eloquent testimony, but a stronger case is made by the rapt and tearful faces of the museumgoers who sat facing her in Manhattan two years ago. The film’s message can be summed up in a familiar phrase: You had to be there.