The 34-year-old star of "Avatar" and "Star Trek" plays pianist, singer and activist Nina Simone in the forthcoming biopic "Nina."
Her casting drew criticism from some, who argued that Saldana bears little resemblance to the singer, who died in 2003 aged 70.
Musician India.Arie said "they should have chosen someone who looks like Nina Simone," and an online petition for a boycott of the film attracted more than 10,000 signatures.
But Saldana said she feels strongly that she's right to play Simone, an immense, irascible talent who made an indelible mark on both music and the civil rights movement with songs including "To Be Young, Gifted and Black" and "Mississippi Goddam."
"The Nina Simone story needed to be told, and I'm really blessed that I did it," said Saldana, a New Yorker of Puerto Rican and Dominican descent.
"I'm human. I wish I was made of steel and so certain things wouldn't affect me," Saldana said at a recent London event to promote "Star Trek Into Darkness," in which she plays multilingual communications officer Lt. Uhura.
"So it did affect me but I couldn't let that deter me from doing what I needed to do.
"Just like everybody else I feel very strongly about Nina Simone, and that (this) was a story that needed to be told.
"I do believe that if everybody had more information about how this all came to be, it might help," she added. "But then again, I'm not here to get the acceptance of people. I'm here to be an artist first."
"Star Trek Into Darkness," the second film in J.J. Abrams' rebooted series, sees Uhura play a bigger role in the action, to Saldana's delight. She even got to do a scene in Klingon.
"They flew in this linguist from San Francisco who gives courses. You go away for the weekend and you just speak Klingon," she said. "It ended up being much easier than I thought."
Like the entire Enterprise crew, Saldana has mixed feelings about Abrams' imminent departure for the "Star Wars" universe. He is due to revive the series with a new film in 2015, so it looks unlikely he'll be at the helm of a third "Star Trek" voyage.
Saldana hopes he'll remain as a producer, with another member of the existing team - possibly one of the writers - stepping in to direct.
She said she wouldn't want to see a new director come in and lose the essence of Abrams' reboot of the series.
"There's been a tone set" with Abrams" movies, she said - "So much so that it's made a fan out of me."
Aha! So is Saldana, like Abrams, a "Star Wars" fan in the "Star Trek" camp?
Neither, it turns out.
"I'm more of a 'Dune' kind of person," she said.
"Star Trek Into Darkness" opens Thursday in the United States.