Though he first photographed the 28-year-old pop star 10 years ago, Shields tells Radar he was particularly excited to embark on the journey again because he and Lovato have "both grown a lot as artists and people" since then.
To make the mesmerizing, black-and-white photo shoot even more special, Demi posed alongside Tyler's girlfriend, actress Allie Marie Evans.
In the images, a short-haired Demi was seen sporting a fierce pantsuit with a lace bra underneath. Everything from the color of their hair to the hue of their lipstick and eyeshadow was dark and sultry, which stood in beautiful contrast to the plain, white wall behind them.
As for Allie, the 25-year-old actress was also seen wearing black. She paired a strappy romper with sexy tights and classic pumps, one of which she perched up on Lovato's left shoulder while the latter glared intensely into the camera.
In another shot, the singer had the tip of the actress' shoe in their mouth.
In perhaps the most stunning photo of all, Demi held Allie in close as the latter stood a few inches above the former, grabbing them by the neck and putting her thumb in their mouth.
Lovato stared seductively at Evans as Shields snapped away.
"About 10 year ago, I did my first [shoot] with Demi, and those photos went everywhere and were viral before that was such the thing that it is today," he told us. "So when they asked me to shoot again, I of course said yes, although this time was different. We had both grown a lot as artists and people, so I was very excited to see where the work would end up and the images that we would make."
Tyler said his leading lady, Allie, met Demi at their "dear friend" Charlotte Lawrence's birthday party, "and that's when the shoot idea was game-planned."
Shields told us it was a dream come true to be able to shoot them together.