BURNABY, British Columbia (AP) — In a former bicycle factory in suburban Vancouver, Amanda Tapping and Jim Byrnes play out a scene before the cameras. It's a typical laboratory, except for one thing: There's no lab, just green. But don't tell Tapping.

"You have to use your imagination," says the fan-proclaimed Queen of Sci Fi.

"No matter whether you have a full set or not, it's your job as an actor to make people believe that you're in that space."

The cast and crew are filming the Sci Fi Channel's new series "Sanctuary," which premieres on the cable channel 9 p.m. EDT Friday with a two-hour episode. Tapping plays Helen Magnus, a seemingly ageless 157-year-old doctor from Victorian England who runs a sanctuary for all manner of "abnormals."

"Anything from the mythology that we grew up with, the little things that go bump in the night, the whispers, the things that you catch out of the corner of your eye. She captures and protects them and studies them," the actress explains.

Adds series creator Damian Kindler: "She protects us, the public, from them, but also protects them from the public at large. But it's also about the fear of who we are and what we might become. We're afraid of monsters and of strange things, but also what those things represent."

"Sanctuary" got its start on the Web in 2007, shot as a self-produced, two-hour pilot by Kindler, executive producer and director Martin Wood, and Tapping, all veterans of Sci Fi's popular "Stargate" franchise. The team soon realised that, with a low budget, going to the places Kindler envisioned in his script wouldn't be possible, except in a virtual world.

"There's no way we can build a massive underground six-story laboratory filled with monsters," Wood explains.

"Just the line `filled with monsters' would turn most studio executives into little blobs of Jell-O. Any time you create that kind of stuff, you can't do it practically."

The solution lay in the use of virtual sets. The actors are filmed in front of a large green screen, with minimal set dressing, if any. The green is then replaced in post-production with fantastic — and stunningly realistic — sets by the show's visual effects department.

"About 70 percent of our sets are virtual, at this point," notes visual effects supervisor Lee Wilson, demonstrating a before-and-after shot — with the actors on green, then with the backgrounds inserted — in his production office.

Wilson and production designer Bridget McGuire will work before an episode goes into production to decide which sets will be built on the stage and which will be created in the computer.

"If it's an office or someplace where the characters will be returning to often, it makes sense to build a practical version on the stage. But if it's an expansive set, like Magnus' laboratory, that's quite spacious and elaborate, then it makes sense to do it as a virtual set."

Directing actors before a green screen — as well as envisioning whole scenes — requires a visual imagination, explains Wood.

"It's something we do all the time when we read books," he says. "What I do on a television set is what most people do when they read a story. I just translate mine into something that everybody can see."

Working without physical sets requires a special skill for actors as well, and Tapping had an opportunity to develop the technique on "Stargate," where she played the popular Sam Carter for 10 seasons.

"The hardest thing with green screen is getting an idea of the scale," she notes.

"If you're supposed to appear to be on the 20th story of a building that's being built standing on a steel girder and the wind is blowing, you have to think: how does your body react to the wind buffeting you when you could fall 20 stories?"

Tapping's popularity among science fiction fans has given her double confidence with the new series. "The demographic is not what people think it is," says the actress, who was mobbed at this summer's Comic-Con show in San Diego.

"It's not 18- to 25-year-old pasty-faced boys in their parents' basements at their computers," she explains.

"I have young girls who were inspired in their classes, whose grades in math went up, come up to me at conventions and say, 'I'm more forward now about my right to learn this and my right to showcase my talent in science.' That kind of stuff will stay with you for life."

Tapping takes her connection with her fans seriously, waiting as long as needed at Comic-Con to meet them at autograph-signing sessions. "She's good with people, and she respects the fans," notes Kindler.

"She respects the fact that she means a lot to them, and she tries to give of herself as much as she can so that they feel that connection. She's incredibly selfless, and that's just really inspiring."

The British native — who now lives in Vancouver — never foresaw herself as a science fiction star.

"I was never a huge sci-fi fan when I started out. I mean, I liked 'Babylon 5' and I liked 'Star Trek: The Next Generation,' but I was more a 'Little House on the Prairie' girl."