Ambler native Josh Singer, a graduate of Upper Dublin High School, has become Hollywood's go-to guy for big-time movies about newspapers.

He won an original screenplay Oscar for his work on Spotlight, and has jumped from there to The Post, Steven Spielberg's First Amendment rallying cry and account of the Washington Post's decision to defy the Nixon administration by publishing the top-secret Pentagon Papers. It hits Philadelphia-area theaters on Friday.

The script was written by Liz Hannah, but Singer was brought in for his experience working on set — The Post was produced in a hurry, with seat-of-the-pants filmmaking that had the two writers delivering new pages daily.

Read more: 'The Post': Tom Hanks and Meryl Streep star in Steven Spielberg's stirring newsroom drama

"This movie was on an incredibly quick schedule. That meant that everyone had to be flexible. You had to be at the top of your game and ready to dive in. The thing that so impressed me about Steven is that he has this game plan, but he's ready to toss it out if it's not working. That's a little scary, but it's also very freeing," Singer said.

"I've found that the best directors create a feeling on set of warmth and a feeling that you have the freedom to play around with ideas," he said. "Working with Steven, you see how happy everybody is to be there. And he's the happiest of all. He's like a kid, and that joy pervades the entire enterprise."

Sometimes, Spielberg was joyous before sunrise.

"It's 6:30 in the morning," Singer said, "and you're on your way to the set and you're getting calls from Steven wanting to know if you can rewrite something."

In one early scene, an anonymous whistle-blower delivers classified papers in a shoe box to the Post newsroom. The original scene had the papers going directly to editor Ben Bradlee (Tom Hanks), but Spielberg had a different idea: to zoom in on the box and follow it, in close-up, as it moved up the ladder of the newsroom hierarchy. That required a lot of additional dialogue, even though most of it ends up as ambient background chatter.

"What you see with Steven is that he uses the camera to emphasize the story, to tell you visually what is going on in the narrative. It's a story about the Pentagon Papers, and in this case, it's literally where he put the focus," Singer said.

Read more: The day in 1971 when the Inquirer defied the government and published the Pentagon Papers

Hannah's script puts much of the focus on Post publisher Katharine Graham (Meryl Streep). As the legal drama of the Pentagon Papers plays out, and the company's lawyers fight the White House for the right to publish, Graham struggles to find enough confidence to assert herself as the head of the operation she's inherited from her husband and father.

"This was a tricky role to write. She needs to be vulnerable but not a victim. She needs to be subtle and quiet but not boring," Hannah said.

Of great assistance was multiple Oscar-winner Streep.

"Beyond her laserlike focus when the camera is rolling, she has an instinct for what is going to work and what is not going to work," Singer said. "You want to up your game because you feel obliged to try to get to her level."

That effort, he said, is repaid tenfold.

"What she gives you is not only different than what you imagined on the page," Singer said, "it is usually 10 times better than anything you imagined on the page."

Hannah said she wants The Post's vision of a woman finding her voice to inspire women to follow Graham's example.

"Katharine Graham was the first woman to be the CEO of a Fortune 500 company," Hannah said. "Today, that number is something like 5 percent. So there's a long way to go."