Critics are loving their first look at Quentin Tarantino's "Once Upon a Time in Hollywood," which premiered Tuesday at Cannes Film Festival and unveiled an official red-band trailer showcasing its leading men: Leonardo DiCaprio as fading movie star Rick Dalton and Brad Pitt as his rugged stuntman Cliff Booth.

The Guardian's Peter Bradshaw raved about the film, which takes place in Hollywood during the summer of 1969, with the murders orchestrated by cult leader Charles Manson being a major theme of the story.

"Quentin Tarantino’s brilliant exploitation black-comedy 'Once Upon A Time In Hollywood' finds a pulp-fictionally redemptive take on the Manson nightmare: shocking, gripping, dazzlingly shot in the celluloid-primary colours of sky blue and sunset gold," Bradshaw wrote.

'Rocketman' first reactions:Elton John musical called 'triumph,' 'fantastic' in Cannes

The Associated Press critic Jake Coyle called the film "more languorous and luminous than anything Tarantino has done before. Radiant w/ affection for Los Angeles and the movies." He gave praise to DiCaprio and Pitt, who are "fabulous, especially Pitt."

Canadian National Post reviewer Chris Knight tweeted that Tarantino's "ode to Hollywood's lost innocence" will "divide critics."

"Heck, I'm divided, and I'm just one critic," Knight wrote. "But I think the side of me that enjoyed it is going to win out."

Film critic Kaleem Aftab called it "the most enjoyable and cerebral Tarantino for some time," with special praise for Brad Pitt, who "steals" the show.

The new trailer shows DiCaprio's movie star Dalton struggling with his action career and having a meltdown after screwing up a cowboy scene.

"It's official, old buddy," Dalton tells his loyal stuntman Booth. "I'm a has-been."

More:Tarantino, DiCaprio to premiere 'Once Upon a Time' at Cannes Film Festival

Dalton's agent, Marvin Schwarz (Al Pacino) is a fan, however, encouraging his client, "All the shooting, I love that stuff."

The trailer gives a good look at Margot Robbie's Sharon Tate, who moves in next door to Dalton, and the man who would be responsible for the actress' murder, Charles Manson (Damon Herriman).

While working on Dalton's roof (in an impressive shirtless display) Pitt's Booth catches the eye of the weakly smiling Manson.

The R-rated film opens July 26.