Magic! It’s what films are all about. Just think about how often the word crops up in cinematic conversation. Visual effects are “movie magic”. People still talk about the “magic of Hollywood”. There’s even a well-known VFX company with the word “magic” in its name.

Portraying magic on the screen requires considerable ingenuity. As a filmmaker, how exactly do you visualise this eldritch and elusive force? Do you stir up a witch’s brew of pyrotechnics and black powder? Do you unleash your best fire and fluid sims?

Or do you forget the light show and focus instead on the way wizardry affects the physical world? Perhaps you abandon visual effects altogether and rely wholly on crafty cinematic techniques to imbue a scene with the appropriate sense of otherworldly wonder.

Ask a hundred people to name their favourite magical effect, and you’ll get a hundred different answers. Here are a few of mine.

Fantasia – Mickey Wakes The Brooms

In the third segment of the classic Walt Disney animated feature Fantasia, Mickey Mouse plays the part of the Sorcerer’s Apprentice. Early in the sequence, his mystical master conjures fantastical images from a glowing skull. In order to communicate its supernatural properties, Disney animators added a pulsating yellow aura around the sorcerer’s hat. When Mickey borrows the hat, similar lighting effects appear round the household brooms he brings to life.

The “magical glow” is such a familiar conceit that it’s easy to underestimate the significance of this early example. Yet I believe Fantasia is the template on which almost all subsequent movies have based their many and varied visualisations of wizardry. How so? Because Fantasia was one of the first films to make a fundamental connection between magic and light.

It’s a connection we now take entirely for granted. It’s also an entirely logical choice. Cinema is light – quite literally. What better way to represent magic on screen than to manipulate the glow of the projector in extraordinary ways?

Mary Poppins – “A Spoonful of Sugar”

Still with Disney, here’s a sequence that contradicts everything I’ve just said. You all know it: it’s the jaunty musical number during which Mary’s magic helps Jane and Michael Banks tidy up their nursery.

During the song, clothes fold themselves into drawers, beds make themselves and the scattered contents of a doll’s house fly back into their proper place … all without a single flash of light or zap of electricity.

Rejecting the “magical glow”, this sequence relies instead on that other cinematic staple: the manipulation of time. This is very much a filmmaker’s solution, exploiting as it does the mechanical principles behind the movie camera in order to alter real-world physics. In short, it achieves most of its effects through reverse action photography (nimbly assisted by a variety of wires and hidden rigs courtesy of the special effects department).

Most modern audiences will know more or less how the tricks were done (as I suspect did many viewers of the time). Yet the tricks still work. Sure, they’re just funhouse illusions, but I’d argue it’s their very simplicity that keeps them both charming and fresh.

The Fellowship of the Ring – “You Shall Not Pass”

There’s plenty of magic in Peter Jackson’s The Lord of the Rings trilogy. But, just as in Tolkien’s novel, much of it is implied rather than overtly stated. In this respect, the films bear as much resemblance to Mary Poppins as they do to Fantasia.

If you think I’m crazy comparing Gandalf to a prim English nanny, consider the scene in The Fellowship of the Ring where he and Saruman come to blows. The two wizards slug it out in a kind of telekinetic fist-fight, with nary an energy beam in sight.

However, the scene that really sells Jackson’s approach to magic is the confrontation between Gandalf and the Balrog on the Bridge of Khazad-dûm. To deflect the giant beast’s blow, Gandalf creates a shining spherical force field. Yet the glow is subtle enough to make you wonder if it’s the magic itself that you’re seeing, or just its effect on the surrounding atmosphere. The same goes for the flashes of light that accompany the wizard’s sword strokes. Magical force or just superheated air? You tell me.

I like this knife-edge approach. Magic should be a slippery thing, hard to see, even harder to grasp. Something you glimpse out of the corner of your eye … and then question whether you ever saw it at all.

Harry Potter

If it’s pyrotechnics you’re after, look no further than the Harry Potter series. In film after film, wizards wield their wands both in battle and in play, generating a bewildering array of energy streams, plasma balls, electrical discharges – you name it. This is magic writ large enough to fill the widest widescreen … and to bring the biggest render farm to a grinding halt.

Subtle it ain’t, but the magic of Harry Potter undoubtedly delivers the sort of visceral thrills only clever conjury can muster. And, like the magic of Mickey Mouse, it’s all done using the primary element from which all movies are made: light.

These are my choices. What are yours? Should magic explode like a fireworks show on the Fourth of July? Or should it creep beneath the surface, working its charms not on your eyes but on your mind?

Is magic light or dark? You decide.

Harry Potter and the Deathly Hallows photograph copyright © 2011 by Warner Bros. Pictures. All rights reserved.