Over the course of eight years President Barack Obama was shadowed by former White House photographer Pete Souza, whose photos captured nearly every moment during the 44th president's two terms. Souza sometimes took 2,000 photos a day. His new book, "Obama: An Intimate Portrait" (Little, Brown), features more than 300 of them.

In the book's foreword President Obama writes, "I probably spent more time with Pete Souza than anybody other than my family in the eight years in the White House."

Little, Brown

Of being a chronicler of history, Souza said, "It was a great privilege to do this job. I felt fortunate that I had the opportunity."

Appearing on "CBS This Morning," Souza was asked if he could pick a single image that best captures the former president.

"It's hard to choose any one," he said. "Certainly some of the ones of him interacting with kids or with his family, but also the more weighty pictures of him in the Situation Room during the Bin Laden raid. So I think the pictures together tell you the most about him than any one picture can."

Co-anchor Charlie Rose commented, "Jim Baker has said about being Secretary of State, you really have to have the complete trust of the president. Is the same thing true about photographers?"

"Absolutely. Absolutely."

"How do you earn that?"

"I think you earn that over time," Souza said. "I was lucky in that I had known him for four years before he became president. I had already established a professional relationship with him. So coming in, I already knew him. That helps. But then over time, you just have to earn that trust, day in and day out."

Souza also got to see the president's sense of humor, as when White House Trip Director Marvin Nicholson, who was dieting, checked his weight on a scale. "He kept sliding the scale to the right, and unbeknownst to him the president's got his toe on the scale," Souza said.

President Barack Obama puts his toe on the scale as Trip Director Marvin Nicholson tries to weigh himself during a hold in the volleyball locker room at the University of Texas in Austin, Texas, Aug. 9, 2010. Official White House photo by Pete Souza

Souza also documented private moments with the Chief Executive, as when he invited a couple of hecklers backstage after an appearance in Austin in July 2014.

"It was an immigration policy speech, and there were these two guys that were heckling him during his speech. And he said, 'Let me finish my speech and afterward you can come backstage and I'll have a private conversation with you.' And that's exactly what he did." [With the Secret Service nearby.]

After an appearance in Austin, President Barack Obama invited backstage two men who had heckled him during his speech, July 10, 2014. Official White House photo by Pete Souza

"The president praised you for being almost invisible; he didn't know sometimes you were in the room," said co-anchor Norah O'Donnell. "Were there ever moments where you thought, This is too personal, I shouldn't be here? Or, There shouldn't be a photograph of this moment?"

"Not when it came to moments of history," Souza said. "With moments with the family, yes, I would try to give him space. Moments of history, I felt I am the guy that needs to be there for everything that happens, so in those cases, no."

A favorite of Souza's photos was of a young boy touching President Obama's head because, he said, his hair looked just like his own.

"The little boy's name is Jacob Philadelphia. He's touching the man who's the president and he looks like him. But it also tells you something about President Obama where he would be willing to bend over like that and let a 4-year-old just touch his head."

Jacob Philadelphia meets the president. Official White House Photo by Pete Souza

One of the most iconic photos of the Obama presidency was the May 1, 2011 image taken in the Situation Room as Mr. Obama, Vice President Biden, and other national security officials gathered to monitor the raid on Osama bin Laden's Pakistan hideout.

Souza had had a week's notice that something would be happening so he could prepare to be present. "We were there all day," he said. "It wasn't just that one 40-minute meeting in that little room; there were meetings throughout the day."

"The thing I like to tell people about that photograph is, you have the most powerful people in the federal government watching as this unfolding and really there's nothing they can do. They've already made their decision, and now it's up to those guys on the ground, and I think that's what leads to the anxiety in all those faces."

President Barack Obama, Vice President Joe Biden, Secretary of State Hillary Clinton and members of the national security team receive an update on the mission against Osama bin Laden in the Situation Room of the White House May 1, 2011, in Washington. Official White House photo by Pete Souza

Rose asked, "What's the essence of taking a good picture?"

"It's capturing a moment, but accurately portraying the mood and the emotion that's taking place," Souza replied.

Since President Donald Trump has taken office, Souza has made pointed posts on Instagram that present a counter-image to whatever news or tweets are coming out of the current White House, such as his August 23 post showing President Obama speaking to the press at the White House Briefing Room. He captions the photo: "How a President normally engages with the press. (Or is it: How a normal President engages with the press.)"

Pete Souza/Instagram

When asked why he trolls Mr. Trump, Souza replied, "The photographs that I post on Instagram now and the words that I write, I think, speak for themselves."