Double Negative provided digital fire when Standish fires his gun and ignites.

"Those were two shots that we prevised early on and actually went to a location and built ourselves a big metal dummy that we could pose and suspended off the rig hanging over the building and set it on fire. And we dressed it up and shot that with multiple cameras. And what was great about that was it gave us all the interaction on the building: all the reflections in the windows, all the moving shadows on the walls, all that stuff came from that plate photography. And, of course, metal being metal, it smashed into the back of the carriage and that's what destroyed the carriage. And after we got those plates, we built a 100-foot tower, and got a stunt man and set him on fire and threw him off the tower and shot that on greenscreen and replaced the dummy in the plate with the stuntman and we also did CG windows. Because we shot the guy for real, it was a lot of fun, there wasn't a great deal of tweaking and noodling those shots in post and people know it's real and don't question it."

However, the digital effect had to match the practical one and so the framing of the fire necessitated a very high resolution as well as the most sophisticated shading and rendering, according to Jarrett.

By contrast, the slow motion exterior explosion uses practical fire, and is Jarrett's favorite scene. "We were on location in Liverpool with Robert and Jude and everybody. That location was real: it was a building that was about to get renovated. We obviously couldn't have any explosions near our actors so we prevised the whole sequence as a slow motion sequence -- 120 frames-per-second. And then we had special effects put air mortars on location, which are these huge cylinders that you can fire air through at really high pressure. And we would have Robert run right past those and replace all of those where the explosions are supposed to be. So that as Robert or Jude would be running, these air mortars would go off and we'd physically blow them and their clothes and you'd get a really strong reaction from this air on them and, of course, they'd flinch and so that's how we got their reactions to these explosions.

"So we filmed all of that on location, no greensreen at all. And then several months later we rebuilt the environment in green, and spent a week with special effects and a motion control camera and reshot those camera moves precisely, blew up stuff and high speed with a motion control camera and then comp'd it in. So those explosions were completely real. I've done CG fire before and it can look great in certain situations but for me, in that situation, where it was slow motion, in particular, where the explosions have to grow organically, I just thought that it would take a lot more effort and not necessarily look as good. So, live action was essential. And we built green replicas of Robert and Jude and often replaced those in the shot, so that the explosions would wrap around those green dummies, so you at least get some sort of fire interaction. And we ended up doing a bunch of CG debris on top of that, and a little CG fire, too, when Robert catches fire."

Another set piece is the ship launch, in which Holmes and Watson are on the run in a ship dock. "We built a set piece of the ship about 20 feet high and 200 feet long," Jarrett explains, "and were able to shoot close up action against that, but when the ship launches, we took the whole set out and completely recreated it digitally, so that we actually did a reconstruction of the building that the ship was in and the ship itself and all the props. It was pretty detailed and had to be big with lots of dynamics in it. There had to be ropes and platforms hanging off it. Once the boat begins to move, everything that supports it is wood and so it had to smash and crash and break. We used a big old dynamic simulation for that. Framestore did that sequence. It was an interesting mixture of shots and everything leading up to that shot was matte paintings."