Inauguration Day 2017 was an emotional day. I had spent eight years visually documenting President Barack Obama’s time in office as his chief official White House photographer, and I was exhausted. I looked forward to a break, but knew I’d miss interacting with him and my White House friends. We had all grown close and would suddenly be separated that day at noon. What made the day surreal was the person Obama was handing the keys over to. It wasn’t Hillary Clinton, as we all had thought. It was a carnival barker who had ascended to the presidency by sheer bravado, bullshit and outright lies.

As our helicopter lifted off, one of my White House “family members” asked me how I was doing. “I’m depressed,” I said. “I watched this guy” – pointing to Obama, seated across from us – “every week in the Situation Room, asking thoughtful questions, listening to advice, making tough decisions on important issues. But this other guy…” I said, glancing out the window to where the new president had watched us depart, “is not capable of that.”

Donald Trump tweets: ‘WITCH HUNT!’ on 27 February 2018. Pete Souza responds by tweeting this picture with the caption: ‘A different kind of witch hunt – Halloween 2010.’ Photograph: Pete Souza/The White House

At the time, I hoped Trump would surround himself with competent people, learn on the job and not lead us down a dangerous path. But his presidency has become a reality game show. He does not respect women, minorities or immigrants. To him, a critical news story is “fake news”. To him, all our intelligence agencies are corrupt. He shuns preparation for meetings with foreign heads of state. He tells his supporters how he alone can fix the economy, yet his policies will hurt them and help line his pockets.

Early in the first week of his presidency, I posted on my Instagram account an innocuous photograph I’d taken of Obama by the Resolute Desk. Underneath I wrote a snarky caption, saying: “I like these drapes better than the gaudy new gold ones” that had recently been installed. I was pissed off that Trump had been elected. I was also appalled by the curtains themselves: the redecorated Oval Office, with its emphasis on gold, made the White House look like his personal palace. In fact, it is the people’s house.

Donald Trump tweets: ‘The real story is that President Obama did NOTHING after being informed in August

about Russian meddling’ on 26 June 2017. Pete Souza responds by tweeting this picture with the caption: ‘On 5 September 2016, President Obama confronted Vladimir Putin about meddling in our election.’ Photograph: Pete Souza/The White House

The overwhelmingly positive reaction to my post took me by surprise – but one comment left me bewildered: “Pete is dropping shade with a comment on drapes.” What is shade? I wondered. During the next few days I posted more photographs of Obama taken during his presidency, using subtle captions that contrasted with something the new president had done. Dozens of reporters asked to interview me. I turned them down. They did their stories anyway. A few wrote that I was “throwing shade” at the new president. Finally, I Googled “throwing shade” and discovered it’s a “subtle, sneering expression of contempt for or disgust with someone – sometimes verbal and sometimes not”. Yup, that’s what I was doing – throwing shade.

And I kept it up for the first 500 days of the new administration, and I plan to keep going. My comments are often humorous, and I’d even say they are more or less respectful. They are certainly more respectful than the tweets coming from Trump. I also try to make subtle comments with my Instagram posts without directly revealing what the current president has said or done.

Donald Trump tweets: ‘We must keep “evil” out of our country!’ on 3 February 2017. Pete Souza responds by tweeting this picture with the caption: ‘President Obama shaking hands after his remarks in 2016 at the Islamic Society of Baltimore mosque and Al-Rahmah School in Baltimore, Maryland.’ Photograph: Pete Souza/The White House

Here you will see some adaptations of my original posts matched up directly with the Trump tweet that inspired them. During the past 18 months, outrage has bubbled up inside me. I have become more and more appalled at the person we elected to represent our nation. Now I’m standing up and shouting out. I can’t be subtle any longer.

Shade: a Tale of Two Presidents is published by Sphere at £25