Opening in 1927 New York, the Magical Congress Of The United States of America is about to render the powerful dark wizard, Gellert Grindelwald (Johnny Depp), from its maximum security prison to London to be tried for his crimes in Europe. But, aided by a follower, Grindelwald escapes. This triggers a series of sinister events in London, Paris and Germany, as Newt Scamander (Eddie Redmayne) and Albus Dumbledore (Jude Law) attempt to take Grindelwald down, whilst facing new threats and conspiracies themselves from a divided wizarding world.

The movie went into physical production in January 2017, with Rousselot joining for cinematographic prep in April. Principal photography commenced in July, and took place over 100 subsequent shooting days, before wrapping in December.

Whilst the final movie is set amongst the towering skyscrapers of 1920s' New York, plus the streets of London and Paris, it involved very little location work. Apart from brief stints at Lacock Abbey in Wiltshire, Highgate Cemetery and Whitehall in London, the Seven Sisters on the Sussex Coast, and central Paris, the vast majority of Fantastic Beasts: The Crimes Of Grindelwald was shot on a series of sets, built on the stages and backlot, at Warner Brother Studios Leavesden, near Watford. The sets were designed by Stuart Craig, with the exquisite wardrobe produced by costume designer Colleen Atwood, both of whom are triple-Oscar winners for previous works.

Given that the cinematographer's key task is turning the script into moving images, Rousselot - whose other credits include Sherlock Holmes: A Game Of Shadows (2001) and Sherlock Holmes (2009), both directed by Guy Ritchie, Charlie And The Chocolate Factory (2005) for Tim Burton, and Shane Black's The Nice Guys (2016) - says he took the only route possible in the circumstance: "To immerse myself very, very slow into the project by talking with all of the key collaborators, and try to enjoy a new voyage of discovery."

For any cinematographer the first port of call is always with the director. "Whilst the original movie was fantastical, and really quite dreamy in places, this story was something fresh and of its own. The task was really to create a new aesthetic that was altogether darker, more sinister, murky and mysterious. But, my initial conversations with David were not definitive statements about doing one thing or another. Rather it was more of a sorting and refining process."

Rousselot says guidance came partly by absorbing the imagery from a huge number of vintage photographs of London and Paris from the period, which were spread over the walls of the production offices.

"You cannot do without references, but you cannot mimic them," he says. "They provide talking points, and a means of communication between you and the director, set and costume designers, and the VFX teams. Actually, my take on references is that you can use them more negatively than positively. By which I mean, you can subtract and avoid things you don't like, so as to arrive at what you really want to achieve."

As with the inaugural movie, so too Fantastic Beasts: The Crimes Of Grindelwald was a digital shoot from the outset. However, whereas the first film combined G- and E-series Anamorphics with Alexa Studio XT, this time Rousselot chose Leica Thalia spherical glass fitted to ARRI Alexa 65, to affect a change to the overall aesthetic.

"We didn't want to go Anamorphic, but did want to frame the production 2.40:1 widescreen again," he explains. "I didn't test other cameras, as I wanted the continuity of look from the ARRI sensors. So my tests with the Alexa 65 were concentrated on evaluating a variety of spherical lenses.

"To be honest, there are lots of brilliant optics on the market today, and I would have been happy with any of the other three that I evaluated. I went with the Thalias, as they are very even from centre to edge, with no loss of focus or distortions. Whilst they are crisp in combination with the Alexa 65 sensor, they are gentle on faces. This meant I would not have use any diffusion on close-ups, and in fact never did. On top of that, the VFX team had an enormous number of effects to create and contend with - strange creatures, digital set extensions, and physical effects, such as flames, smoke and explosions. They were very happy about having lots of clean-looking pixels to play with in post, and was I glad to make their job easier."

Highlighting his work with the VFX team, Rousselot says, "There was quite a lot of pre-viz for the VFX sequences, such as the dramatic carriage chase around the New York skies and cityscape. I made some suggestions here and there, and I would have voiced my dislike to a scene, but I don't recall ever doing that. Christian and Tim are excellent at what they do. I like them and trust them too, so there was no reason to interfere."

A particularly close collaborative effort was required for the scene in which Newt and Dumbledore walk through the smoggy centre of London, as Rousselot says there was no practical way to achieve such an intense level of murkiness on the actual streets.

"If we took perhaps one cue from the old reference photos, it was images of the real pea-soupers London experienced in that period. We knew we would have to recreate that look on stage," he explains. "In practice, we took the longest stage at Leavesden. The art department provided foreground pieces and elements of sets - the roads, walls, bits of statues, and portions of other landmarks, such as Trafalgar Square. We pumped in a combined mixture of smoke and fine water particles to create a foggy atmosphere, with points of light added to establish a sense of perspective. The VFX team then did the rest, combining the live action with all sorts of other set extensions and digital artefacts. But you would never see the join."

As for the lighting, Rousselot considered the set plans and models very carefully during prep, in liaison with gaffer Chuck Finch, to decide where the fixtures would be placed. Lighting was supplied by the Warner's on-site facility at Leavesden.

"Although I went with normal Tungsten illumination on the previous production, we used many more LEDs, such as ARRI SkyPanels, this time round, to flood the massive sets. They allow great control over the amount, colour and temperature of light, but without burning the set down. Obviously, you need to control the volume and shape of the light on faces. Whilst quality of LED fixtures is getting better for that, I still used Tungsten illumination on the close-ups, as well as LEDs, but never felt we had to visit the hardware store for candles or bulbs."