The photographer this year was in Italy to capture behind-the-scenes moments with the celebrities in town for the Venice Film Festival.

Dakota Johnson, Rami Malek, Jake Gyllenhaal, Kristen Stewart, Timothée Chalamet, Anya Taylor-Joy, Zendaya and more have all been subjects of Williams’ unposed portraits.

Explaining how he manages to capture such moments and a rarely seen side of so many famous faces, Williams told Newsweek that it’s all about encouraging spontaneity.

“I don’t go in with a fixed image in my mind when I start a shoot. I like to allow for the spontaneity that you only get from collaborating,” he said. “When you get to work with some of the greatest artists of our generation, and you are collaborative, you get so much more than you could possibly come up with on your own.”

Williams said he started taking photos as a young child and now has his technique very well figured out.

“I started taking pictures when I was 6 years old and I’m now 49. So after 43 years, I think I’ve got my process pretty efficient,” he explained. “I work very, very fast. And I no longer question where to put the camera, I know exactly where the camera should be to take the picture that I have got in my mind in order for the happy accidents to happen, that in turn create the best pictures.”

Luck and being in the right place at the right time is crucial but Williams makes it all come together with his practiced skills. He is also present in his photos as his subjects interact with him.

“You need to be lucky, but you need to be in the right place to best record that lucky moment, when it happens. You need to have an understanding of ambient light and know what small changes you may need to make to the angle of someone’s face in order for that light to work best. And these are all calculations that you make in split seconds,” he said.

“And they come from having done it for a very, very long time. The other element is that I’m often a participant in the photographs that I take. So you can sort of sense me in the photos, you’re aware that there’s a character behind the camera, as well as the one in front of it. You can see that in a lot of my pictures, the subjects reacting to the person behind the camera.”

Here are six of Williams’ favorite shots:

Ultimately, to capture his celebrity subjects in candid moments, Williams is a big believer in not treating them like celebrities.

“Don’t treat them like celebrities, treat them like people, I’m always trying to find the person behind the personality. So I talk to them, like I talk to my mates,” he said. “And I encourage that side of them, I lead from the front, I’m playful when I’m taking pictures, but I also make my subjects feel safe.

“And I don’t think I’ve ever made anyone regret that trust they’ve put in me.”

Newsweek interviewed Greg Williams as part of the launch of the new MARTINI campaign #MARTINIMOMENTS.