Kate Winslet spent the better part of a decade trying to bring the story of war photographer Lee Miller to the big screen. As lead actress and producer, Winslet’s dedication to the project is evident as she crafts one of the strongest performances of her career and one that should lead her to many nominations come awards season. Unfortunately, her excellent work is surrounded by such a conventional biopic. Based on Antony Penrose’s book “The Lives of Lee Miller,” Ellen Kuras’s “Lee” fails to match the unbreakable spirit of its subject, although it holds a lot to admire.

Lee Miller led a remarkable life and did so on her terms. As a woman, she was a strong nonconformist who embraced her individuality and soaked up the bohemian lifestyle. A former model, she became a photographer whose focused eye captured powerful images that held an essence of truth quite unique to the photojournalism of the late 1930s.

Miller lived in France with a tight group of artistic friends. Her closest pals are Paul and Nusch Éluard (Vincent Colombe and Noémie Merlant) and Solange D’Ayen (an underused Marion Cotillard). The film doesn’t allow time for the audience to experience the depths of connections Miller has made with this group. In later scenes, once the Nazis begin their destructive push, the bonds of friendship should have elicited deeper emotions but remain dramatically flat due to the lack of character building.

Cotillard is the biggest victim. Existing as the most underwritten role in the film, we barely realize D’Ayen is there, let alone her deep friendship with Lee. Sidelined for most of the film, Cotillard is brought back for a supposed emotional reunion, but the screenplay fails her. An actress of her caliber deserved something better than existing as a mere caricature.

Lee meets a posh Brit, Roland Penrose (Alexander Skarsgård), who will become her future husband during her time in this den of free spirits. Skarsgård is a fine actor but finds himself miscast in this project. He cannot grasp the accent, while his performance (and how his character is written) is aloof. The script doesn’t know what to do with Roland, giving any deep character development the shaft. It isn’t made clear how these two souls find such a deep connection beyond their sexual attraction, and that is a shame, as Winslet and Skarsgård certainly have chemistry.

Miller finds a position at British Vogue, but her efforts to get something tangible published are met with opposition. Audrey Withers (Andrea Riseborough) recognizes the value of Miller’s talents and fights for her photographs to receive publication, though a male superior presumes that a woman should shoot pictures more suited to the female lifestyle.

At the time, women were not allowed anywhere near actual combat, especially on the front lines. Lee’s mettle and unshakeable drive cuts through the sexism of the time and finds her in the middle of some of the most critical moments of WWII. She is on the battlefield, capturing the combat and humanizing the many severely wounded soldiers. In two of the film’s most affecting moments, at the end of the war, Lee and her friend and fellow photojournalist, David E. Scherman (an excellent Andy Samberg), capture what remains of the concentration camp Dachau and spend a strange night in Hitler’s apartment.

These two devastating scenes are the best in the film. The full tragic weight of the Holocaust comes into focus and nearly breaks Lee, while David (who is Jewish) cannot fathom what has been done to his people. There is a heart-wrenching power within these moments that is lacking from the rest of the film. Our heart breaks for David and for Lee, who doesn’t have the ability to take away her friend’s pain but knows she must continue to shoot and get these dark truths out to the world.

The screenplay (written by Liz Hannah, Marion Hume, and John Collee) captures Lee Miller’s pioneering spirit and unbreakable drive but leaves little of a lasting dramatic or visual impression. Director Kuras moves from one important moment of Miller’s life to the next without any discernible style. Cinematographer Pawel Edelman’s camera shoots everything too flatly, whereas a film about the power of the image should have found strength in its visual palettes. Mikkel E.G. Nielsen’s editing looks cobbled together. It does nothing to enhance the dramatic effect of Miller’s story, as scenes merely begin and end, causing the film’s stronger moments to feel too often fleeting as they struggle to make an impact.

Too many narrative threads are left unexplored. One of the most important is Lee’s relationship with her son, Antony (Josh O’Connor), which is given a paltry treatment. The framing device of their conversations is such a droll and manipulative gimmick that it becomes insulting to Miller’s legacy.

Kate Winslet’s toweringly excellent portrayal grounds “Lee” while the film suffers from its by-the-numbers presentation of such a full life. The actress is the most adventurous of her generation and is skilled in finding the raw emotions of her characters. Winslet’s work encapsulates the defiant spirit that made Miller such a unique persona but considers also the fear and uncertainty that made her human. This terrific performance will go down as one of Winslet’s finest.

In her feature-length directorial debut, Ellen Kuras has a tough time keeping her head above water. She loses grip often and fails to sustain the drama that comes from the events that surround and shape Lee Miller’s life. While there are moments that hit, too much of the film is matter-of-fact in its presentation, a flaw that ultimately hurts the final product.

“Lee” is a film to see for Kate Winslet’s exceptional performance, and Lee Miller’s incredible life is too meaningful to ignore. Unfortunately, the film’s lack of cinematic ambition causes it to be mundane and even conventional.