Photojournalist Pete Souza, 64, served as White House chief photographer for President Barack Obama for eight years, and previously as White House photographer for President Ronald Reagan. Souza’s latest book, “Shade: A Tale of Two Presidents,” contrasts the Obama and Trump administrations by juxtaposing photos of the former with tweets, quotes and headlines generated by the latter.

These last couple of years, you’ve gone from being an observer and documenter to now sharing your opinion and being a part of the political conversation. Are you someone who has been political in the past?

I was never really active politically. It’s just more one of those things that you take certain turns in your life, and you sort of end up where you end up. And in my career, I ended up covering politics a lot. But I’ve become more active, post-White House, just on my Instagram feed, which is not anything I would have ever expected I would be doing.

It helps to have observed two presidents from two different political parties. Both of whom I thought were decent human beings, and both of whom I thought understood what it meant to respect the office of the presidency. And then this guy comes along, who I think disrespects the Oval Office every day. Lies to us all the time. Bullies people. I felt I had a unique voice and that I couldn’t just sit by and not do anything. I don’t know that I could have lived with myself if I didn’t speak out.

I wouldn’t be doing this if Mitt Romney was president, if John McCain was president, Jeb Bush, John Kasich. This is not a partisan thing. It’s a citizen thing. And I’m trying to do it in a somewhat humorous way.

Do you remember what first started you off?

Yeah, it was a couple days after the inauguration. There was a picture of the new Oval Office that I saw somewhere. And it was those gold ornate curtains and multiple flags. I was appalled. Like, “What is this?” This is not the Trump Tower gold palace. This is the Oval Office, you know? And so I posted a photo of President Obama seated on the Resolute desk with the curtains that he had. I think my caption was just something like, “Kind of like the old curtains better.” And I may have said, “don’t you think?” I can’t remember. So there was a double meaning there. People picked up on it right away. Somebody even used the term “shade.” Which I didn’t really know what it meant. And I was like, “Oh, maybe I’m onto something here.” And then there was the Muslim ban. And I posted something on that. Clearly, I had struck a chord. And I was just off and running.

And it’s become hugely popular.

Yeah, I ran into a congressman the other day. And I introduced myself to him. And he goes, I know who you are. I said, “Well, I just wanted to thank you for what you’re doing.” He goes, “Well, I want to thank you for what you’re doing.” And I was just kind of taken aback, you know? I sort of forget the power of Instagram at times. It’s crazy: I have more than 2 million followers. I mean, I’ve worked for four newspapers in my career. The combined circulation of those four newspapers does not equal the number of followers I have.

That’s sobering. So, did you feel uncomfortable sharing your opinions after doing the opposite for most of your career?

Well, when I first started doing it, it was so subtle that, unless you were really picking up on the news, you might not know what I’m talking about. Then last spring, I decided to take it further and do the “Shade” book. I think part of it was getting hate mail, a couple death threats. It’s, like, “Screw you, man. You’re not going to shut me up.”

Having taken those photos as a sort of historian, documenting history — and given access under those terms — does it feel fair to use them in this way?

Some people say they thought it was unbecoming of me to be doing this. That I was supposed to be a documentary photographer for nonpartisan purposes, to document the presidency for history. And that I shouldn’t be speaking out politically. I get it. It’s totally fair to respond that way. But I fundamentally disagree with that argument. These are all public domain photos. I’m a citizen of the United States. I feel strongly about this, about speaking out, about doing something. And I’m going to continue doing it.

And it's also hopefully a reminder, or maybe even in some cases an education to really young people, that what's happening now is not normal. This is not the way the president of the United States should behave.

Do you have a shot that got away?

Nothing that haunts me. Because, you know, I put so much into it. My goal was to create the best photographic archive of a president that had ever been done. And if I missed something here or there because I was a split second too late or I was at the wrong angle, I think in the totality of it, it's not that big a deal. Reggie Love, who was [President Obama's] body guy for the first three years, will not let me forget that when his former coach [Mike Krzyzewski] came to visit one time, I got all these pictures of President Obama and Coach K together in the Oval Office. But I didn't get one with Reggie in it. So that's the picture I missed as far as Reggie's concerned.

How about advice to live by?

You got to show up. Especially with photography, you got to show up if you want maybe some chance of making a good picture. But if you don't show up, it ain't going to happen.

When you get to be my age, you start to really look back at the decisions you made in your life and how it changes where you end up. To have gotten a job with President Obama, you go back to decisions I made 35 years ago. If I hadn't done that or that or this, I don't know that I would have ended up here. I happen to be working with the Chicago Tribune when he gets elected to the Senate. I mean, maybe I would have been successful doing something else if I had taken a different turn, but I wouldn't have ended up as the White House photographer for Barack Obama. Look, I'm not the best photographer in the world, but I was the best person to be his photographer. I'm convinced of it. I knew him four years before he became president, had [previous] experience in the White House, the ability to sort of be invisible when I needed to be. It's like the stars just sort of aligned.

This interview has been edited and condensed. Follow KK Ottesen on Twitter:  @kkOttesen .