Sherlock Holmes: A Game of Shadows has 1,200 vfx shot for a 'non-vfx driven' movie. All images courtesy of Framestore.

"Well, I'm sure you can imagine that we're bigger and better than last time," admits onset VFX supervisor Chas Jarrett about Sherlock Holmes: A Game of Shadows, in which Robert Downey Jr.'s Baker Street sleuth faces arch nemesis Professor Moriarty (Fringe's Jared Harris). "Our new story takes us not only through the London we saw last time, but out into the country by train, across the channel by steam boat, to the French countryside, Paris -- above and below -- then to the industrial heartland of Germany and finally across the snowy Alps to Switzerland.

"We have around 1,200 vfx shots, which, again, for a 'non-vfx driven' movie, is quite a chunk. And we were following in the footsteps of the previous movie and we all had a cool vocabulary together among the returning crew. And I personally thought there were some places where we could up the ante. So this was about how to grow the film rather than reinventing it."

Meanwhile, the work was divided between Framestore, MPC (which used its Tapi tools for dynamically breaking CG objects for destruction such as a high tower) and BlueBolt.

The sequel reinvents how the slow-mo fights of the original were done.

Jarrett says the use of high-speed digital camera was something they wanted to continue as a visual language. In fact, there were a couple of standout scenes where they came to grips with the technology far more than on the first film. "For me, in particular, that would be the woods sequence as [Holmes and Watson] are escaping from a munitions factory in Germany, which is mostly a CG environment," Jarrett continues. "And they break out into the woodlands, which we found on location in England. It's an interesting sequence because we knew we wanted to play with some of the same visual trickery that we had from the first film, but we wanted to amp it up a bit. So we ended up experimenting with very, very high-speed camera track, about 50 feet a second. And we mounted two Phantom cameras on the tracks at the same time but with different lenses. This meant that we could pop out or crash zoom in to a close-up at will in post-production. So we were also shooting at 1,500 frames and could drop down to super slo-mo if we wanted. And there's a cool shot of Watson running and he just jumps over something in his way, and we shifted to slo-mo just as a bullet clips his waistcoat and you see the ripple. It's nice putting Watson in that kind of danger, and using the high-speed is good for that. It's not that complicated. The bullet is real and it's fired from a real gun and hitting a real waistcoat but shot on a greenscreen as a separate element, and then tracked in to his body shape. And so that gives a real natural look to the way the cloth moves. But there's very little CG. We tried to rely on real elements, compositing and well executed tech bits.

For the whole movie there were a huge number of environments, all of which were set extensions, except for the woods, which were CG. Baker Street was again shot on a backlot at Leavesden Studios. A single row of 10 houses was extended into a full city view, across the rooftops. For the first time we see the North and East views from Baker Street (not seen in the previous movie). These shots require extensive motion control shoots to populate the streets.