To catch official White House photographer Pete Souza for a chat might be almost as tricky as to try to reach his boss. His schedule usually mirrors President Obama's, from foreign summits to saluting caskets of fallen soldiers, official meetings and town halls, soup kitchens and golf games. Souza admits he doesn't really have much of a life outside of his work.

Not that he is complaining, though. "I don't have bullets flying over my head, or rocket-propelled grenades coming at me. I do not have to deal with things that I occasionally had to deal with when I worked at the Chicago Tribune. The hardest part of the job is only that it's basically non-stop,” he says.

The White House photographers are responsible for plenty of memorable pictures - some solemn and reassuring, such as Cecil Stoughton's image of Lyndon Johnson’s swearing-in following the assassination of President John F. Kennedy; some very personal, such as President Reagan comforting his wife, Nancy, following her breast cancer surgery.

Some of them are even a bit mischievous, like President Johnson singing with his dog Yuki, or First Lady Betty Ford posing on the cabinet room table of the White House.

Different presidents had different approaches towards their photographers. One might offer his photographer a drink, another might ask him to leave the room at an especially dramatic moment.

White House press say that Souza is "part of the inner circle, no one questions his access, it's just a given", although there are some grievances when the White House releases photos by the official photographer of an event that the pool was not allowed to cover.

He maintains friendly relationship with other press members, but most likely envy the fact that the oval office waiting room is jokingly called his second office.

Souza earned his opportunity, documenting the young Senator from Illinois for the Chicago Tribune, taking shots of Obama at the Red Square in Moscow, where no one recognized him, and across Africa.

By the time Obama was elected President, Souza had already produced a book - The rise of Barack Obama - and secured Obama's trust.

Although he admits he originally planned to be a reporter, not a photographer, and only got his first camera well into his college years, he achieved success relatively quickly, and spent five and a half years documenting Ronald Reagan's presidency.

Following Obama's election, Souza took a leave of absence from Ohio University's School of Visual Communication where he taught, and moved to the office on the ground floor of the West Wing of the White House.

"It's kind of just below the foyer outside the Oval office. So basically I just run up the stairs, turn the corner, and I am at the Oval office," is how Souza describes his routine. "I usually come in around 8 A.M. and he (President Obama) comes in around 9 or 9:30 A.M.. I am pretty much with him all day, until he goes to dinner at 6:30 or 7 P.M.”

I have other photographers; they cover the First Lady, the Vice-President. And if the president has a public event, I position some of the photographers where the press is set up - because that's where the best pictures come out,” he says.

“I don't work every night. Last night he had dinner, but I sent one of my guys to do it, because I had personal engagement. But I work most of the weekends as well,” he adds.

He might have his own seat on Air Force One, but he always has to walk fast or run, to take pictures of the President greeting or being greeted.

"I use to tell people I am trying to create this visual archive of history, so 50 years from now people would look back, and look at these pictures,” Souza says.

“And then someone uncovered a slideshow that Yoichi Okamoto, President Johnson's photographer, had done, I think right after Johnson left office. And he made the same observation, that he's trying to document for history. But instead of saying 50 years, he said 500 years,” says Souza.

“And it made such an impression on me. when I heard his saying that it made me appreciate and value what I am doing more than before, probably. Because I realized that, wow, we are talking not only 50 years from now - maybe hundreds of years from now, people will be looking at these photographs,” Souza adds.

“That makes it all the more important for me to take these pictures, to try to document this presidency for history."

Souza likes Okamoto's pictures: "He had a unique character with L.B.J., but he also was a great photographer, he really tried to document for history, and he set the bar really high. His work is the one I look up to and admire. But I try not to emulate anybody."

- At some point, do you lose that feeling of: "Wow, I am taking another historic picture"?

"I do this every day, shooting 500-1200 pictures a day, but there are still certain times when big things are happening, and I feel real fortunate to be in this position. Those are times when you really feel that you are documenting history. And for me, that's why I am still on this job - to be able to document his participation in history, it's a real unique position for me to be in,” says Souza.

President Obama called him "friend", and Souza says for him "it's important to maintain a good relationship with everybody on the staff. It's a professional relationship. I respect them, they respect me. And they understand the value of what I am doing. That makes it much easier for me to work. I think it's also very important to know the specifics (of the events) because it may influence which people you include in the photo and which you don't," Souza says.

Souza claims he "pretty much" doesn't have any limitations in terms of taking pictures, but points out that it's not the photo team's decision about what pictures are released.

"My main function is to create this archive for history, and there are occasions when the press office wants us to release a photo. We edit the photos, but ultimately they make the decision on whether pictures will be released or not," he says.

He admits there are some ground rules involving pictures of the President's family, "but one thing that I don't do is talk about it," he says.

The White House workers love Souza's "jumbos" - photos hanging on the walls in the West Wing. Some are replaced pretty quickly, others remain up for longer.

- Did you ever try to stage any photos?

"Everything that I do is spontaneous and candid, with the exception of - he does some posed photos, but it's very obvious - people are looking at the camera, they are standing in front of the desk of the oval office. But except for these photos, everything I do is not staged. It's just as it happens,” says Souza.

“He (President Obama) has gotten used to me being around, I try to move around with a small footprint, I don't have noisy cameras. And the staff got used to me being around, they sort of expect me to be in the room. They basically forget about me," he says.

- Almost every photographer thinks about the pictures they didn't take. Does it happen to you, too?

"I take so many pictures, that if I did miss something - I do realize it for the day, but I can't dwell on something I might have missed. I try to put myself in a position every time if something interesting is happening, I am in the right place to make a good photograph. Do I do that 100% of the time? Probably not," Souza says.

And how does he get along with the White House pool? Are there any tensions over his level of access to the President and the First Family?

"Well, this happens with every administration. I am in private meetings, situations that it will be impossible for press photographers to be in - even to clear in, security-wise. My role is to document these private meetings for history, I am not doing it for the press.”

“The press has very different role. In terms of their access to the president, that's determined by press office, not by me. I think I am on good terms with many of the photographers. And when the press office does cramp the behind-the-scenes access to photographers, on occasion I do everything I can to help them to get what they need," he says.

- One of the Netanyahu's visits is best remembered for the photo-op that didn't happen - there was much speculation about whether he was snubbed and "punished". How do you deal with such situations, when you probably do take the picture, and it is not released?

"Oh, I am not going there!” says Souza. I can only say that those are always interesting and potentially historic meetings, and I am just trying to do the best job that I can documenting them.”

Sometimes Souza's pictures have unintentional consequences. One of these pictures featuring Obama Administration officials intensely following U.S. commandos conducting a raid in Abbotabad, during which Osama bin Laden was killed. The yellow tie of one of the officials helped to identify the CIA analyst who hunted bin Laden.

Another Souza's picture that got much attention was one he took in summer 1988, during President Reagan's visit to Moscow. In that picture, Reagan is talking to some tourists at the Red Square, among them a young blond man with a camera. Some claimed the young man is none other than the young KGB agent Vladimir Putin, who was sent with other "tourists" to greet Reagan.

- Was it Putin at the Red Square?

Souza hesitates: "It's something that happened a long time ago, and I wasn't the one who said it was Putin - it was somebody else."

Souza certainly has pictures he's taken that he likes - but he also always stresses his favorite picture is the one he'll take tomorrow. No one knows what will become the future iconic picture of President Obama, but Souza is working hard to make sure history has enough stock to choose from.

***

Some of the photos taken by Souza and his colleagues end up on the White House first-ever Flickr account, another decision meant to project the openness of the administration, which allows almost immediate access to pictures that once could only have been dug through in the physical archives.

It should be remembered however, that as casual as some pictures might look, they were still chosen by the White House public relations team. As some White House correspondents point out, the number of photos available on Flickr does not necessarily correspond with the number of presidential press-conferences, and the White House guards its messaging pretty zealously.

"It's not only an historical tool. It allows the White House to give the taxpayers a window to their world," says presidential historian Professor Douglas Brinkley. "Pretty much since Abraham Lincoln, the American presidents had their photographs taken to make their image both folksy and statesmanlike.”

“Photography has been an important tool for presidents to succeed. Almost every president had his favorite photographer, it became a tradition. Usually the iconic photographs taken are those that humanize presidents, at some moment of rest with the family, or at work, not those of the official meetings,” Brinkley says.

“For historians, it's a great tool too to get a sense of what was going on, because many times the White House photographer photo is the only one taken of historic events at Camp David or the Oval office, where it will be impossible to have hordes of press,” he says.

In addition to “those few photographs published, there are many, many more in the archives, and for historians like myself, it's a treasure trove, an invaluable primary source. It's a truly privileged window." Brinkley adds.

Brinkley thinks White House photographer David Hume Kennerly, who took relaxed pictures of President Gerald Ford and his wife at a barber shop and other unofficial locations, had the closest access to a president.

"Kennerly was a young photographer who was akin to son to President Ford - other photographers never got so close,” he says. "There is no one golden rule, but you probably need chemistry between the President and specific photographer. They are sharing a lot of time and space together.”