"This was a problem," Ellis suggests, "because we'd need a lot of light hitting our subjects and all of our rewind scenes occurred at night or indoors. [DP] John Seale and our VFX [DP] Peter Talbot came up with a way of boosting the scene lighting universally by 2 to 4 stops. It meant that the rewinds could keep the same lighting feel with shadows and highlights matching the forward action but give us the best possible images to work with.

"So it was really the transition in the shoot schedule from forward action to rewind action that took the longest time to set up because we had to accommodate this boost to the lighting. As soon as we had the first rewind set-up in the can, the others followed much more quickly. We carefully planned the position of each camera and marked up the set accordingly, so we were quickly able to set-up our cameras for each shot. "

As for the differences between the rewind sequences, Ellis says the first two involving Dastan (Jake Gyllenhaal), which come right after the other, were the most challenging. "We see time slow down to a freeze, we see the ghost very closely with magical sand particles flowing straight into the camera and we get a really good look at all the component parts of a rewind scene."

The third rewind happens with Dastan and his brother Tus (Richard Coyle). This presented its own challenges. "A very ornate 3D background had to be built and lit," Ellis continues. "We also had a difficult camera takeover as the dagger is pressed between a conventional stedicam shot and our full nine locked camera array. We had the stedicam spiral out from the dagger while running nine cameras at the same time, the operator had to cleverly squeeze between two cameras in order to exit the shot."

The fourth Rewind happens in the Oasis as the group is attacked by snakes. "It was a much faster paced action scene, which actually kept this scene simpler," Ellis observes. "Reduced length and travel of camera moves meant that we could use [fewer] cameras in the array. In this scene, we worked closely with Framestore, which created the snakes. Maya scene files and rendered elements were passed backwards and forwards between the facilities."

Fortunately, there was no magical dagger required for that.

Bill Desowitz is senior editor of AWN & VFXWorld.