The Wicked Witch (Margaret Hamilton), Dorothy (Judy Garland) and the good witch Glinda (Billie Burke) pop off the screen in the 3-D version of “The Wizard of Oz.” (WARNER HOME VIDEO)

So often 3-D is a dispensable alternative, a way for studios to squeeze more money out of ticket buyers while adding little to the movie-going experience beyond red imprints on the sides of each spectacle-wearer’s nose. There are some imaginative exceptions, including the dance documentary “Pina” and the forthcoming “Gravity,” which uses the technology to convey the nightmare of being lost in space. Add to that list the reissue of “The Wizard of Oz,” which screens at IMAX theaters for one week ahead of its 75th anniversary DVD release.

According to a short video that IMAX made, converting the 1939 classic about a girl’s adventures in a fairy-tale land to 3-D was arduous. The first part of the process sounds reminiscent of restoring an old painting: After transforming film reels to a digital format, the movie’s images are sharpened, and colorists remove dirt, scratches and imperfections from years of wear and tear. Then the stereo conversion begins, which consists of isolating individual objects in each frame and layering them to give a sense of depth. “The Wizard of Oz” is the oldest film to get this treatment.

The result is quite stunning and a lot less gimmicky than it could have been. The 3-D elements are subtle; what’s more noticeable is the clarity of the picture. Small details like Judy Garland’s freckled face and the Cowardly Lion’s carefully coiffed curls come into sharper relief. Each gem in Dorothy’s ruby slippers appears to sparkle individually at different times. Technologically, the third dimension doesn’t create too much of a wow factor — for example, the poppies didn’t pop nearly as much as one might expect — but there is a kind of deference shown to the fantastical film that has been a childhood staple for generations.

Seeing “The Wizard of Oz” on the big screen also offers an opportunity to consider the incredible special effects, considering the film was shot more than seven decades ago and long before computer-generated imagery. The black-and-white scenes of Dorothy battling against the wind as a twister approaches were especially transporting. And Toto’s impressive training all but ensures that another generation of kids will be clamoring for a Cairn terrier.

The only negative aspect of getting such a close look at the film is that some of those special effects fall apart under close inspection. The Wicked Witch’s green face looks more like makeup, and the quick cuts that allow the legs of the witch’s deceased sister to curl up and disappear under Dorothy’s house are more noticeable.

But “The Wizard of Oz” taught us that peeking behind the curtain doesn’t have to be a letdown. Even when the fantasy turns out to be the ministrations of a regular old human being, the magic remains.

PG. At tk. Contains some scary moments. 101 minutes.