Head shots, too, are no longer reliable. Ms. Marin said she sometimes checks AwfulPlasticSurgery.com, a celebrity Web site that chronicles the surgically enhanced, to confirm suspicions about who has done what. When Ms. Alessi was casting “The Curious Case of Benjamin Button” in 2007, she received hundreds of head shots. Some of the actresses who arrived for auditions, though, looked nothing like their photographs.

Image Credit... Matthew Richardson

“They would have these huge puffy lips and frozen foreheads,” she said. “You said to yourself, ‘Oh, I can’t use you.’ I don’t mind if they do a tiny bit of something, but it can’t be obvious.”

An actor can even lose a role if a director suspects surgery, whether it was performed or not. John Papsidera, a casting director for the “Batman” movies, said he and a director (he declined to say which one) recently debated whether to hire an actress in her early 20s to play a teenager falling in love. The actress was talented and naturally pretty. But what stopped the director was his suspicion that, at such a young age, she already had breast implants.

“We looked at film where she was topless and it was like, ‘Maybe,’ ” Mr. Papsidera said. It wasn’t a period film, so authenticity was not an issue. Instead, the possibility of implants became “a point of reference,” he said. “It was more of, ‘Where is that person coming from as an actor?’ ” She did not get the part.

To outsiders, such conversations can seem almost cruel. Youthful perfection is prized in Hollywood despite the seeming canonization of older actresses like Meryl Streep, Helen Mirren and Betty White. But a talented 35-plus actress who has had particularly good surgery can still find work. At that age the backlash is not against plastic surgery or Botox itself — everyone seems to be doing it, right? — but its poor execution.

“Behind the scenes, you have so many conversations,” said Mr. Levy, the director, referring to his discussions with studio executives about leading ladies. “Why did she do that to herself? She was beautiful. She was great. But now we can’t cast her.”