I don’t believe I’m saying this, but I attended a presentation at the Science Museum of Minnesota, and they spoke poorly of prisms.

No, they didn’t trash prisms in general — a representative from IMAX simply pointed out the limitations of prisms as commonly used in digital projectors. Light passing through prisms is slightly diffused, and the mirrored chips pressed up against the prisms can only be cooled from one side, limiting how large and powerful they can be.

IMAX has solved that problem with a new series of projectors that use lasers. No prism, no problem: you get a big, sharp image. You’ll want one of those if you plan to project a digital image on a giant domed screen — in fact, you’ll need two, and then you’ll need a giant computer to coordinate the two projectors to insure that the image gets in focus and stays in focus even as heat and other factors threaten to throw the two projections out of sync.

What I’m saying is that converting an Omnitheater to digital projection, to borrow a phrase from Han Solo, ain’t like dusting crops. It’s such a complex proposition, in fact, that no giant dome screen in the world currently uses digital projection for a full-size picture such as we’re used to. Minnesota’s Omnitheater will be the first.

The Omnitheater is currently undergoing beta testing for its new digital system: major parts of the system are in place, but other parts (including the Science Museum’s own projectors, and the computer that will coordinate them) have yet to arrive. On Tuesday morning, I saw a demonstration of the new system in progress, and believe me, you’ll notice the difference.

There are unique challenges to projecting an image onto a domed screen. For one thing, the image needs to be adjusted so that it appears on the curved screen without noticeable distortion. SMM’s current Omnitheater, like the 50 or so similar theaters in the world, accomplishes that with a fisheye lens installed on the projector, which sits in the “doghouse” at the center of the seating area.

The new digital system will be located, instead, in a newly-expanded projection booth at the top of the seating area — more like a conventional movie theater in that sense, which it can be because the projectors’ software can digitally adjust for the screen’s curvature.

Then, there’s the problem of contrast. High contrast is a holy grail for any projection system, and it’s particularly crucial for dome screens, which bounce light not just back onto the eyes of the audience but across onto other parts of the screen — thus, washing out the image. The higher the contrast is, the less stray light there is and the better the picture looks. Here, digital makes a huge difference. The newest IMAX projectors have contrast levels that are unprecedented for the format.

That all sounds very eggheaded, and of course it is — but the difference between formats was apparent in the comparison I saw on Tuesday. First, we watched nine minutes of the 1998 film The Greatest Places: a new print projected from the Omnitheater’s existing film projector. It looked great, which was no surprise. It’s the technology we’ve been watching in Minnesota for 38 years, and when was the last time you complained?

Then, the IMAX team switched over and showed us the same nine minutes in digital. The two borrowed projectors aren’t yet in sync, so they weren’t able to cover the entire dome, but we saw a picture covering most of the dome, and the difference was dramatic.

The film’s opening titles appeared with increased crispness and steadiness (though great pains have been taken to keep the analog projector still, it nonetheless wobbles perceptibly compared to the digital projector). The color saturation was better, and the high contrast meant that Baobob trees that formerly appeared reddish-grey now looked black with shadow against the Madagascar sun. In an overhead shot showing striated rocks, the detail was much more apparent.

The Greatest Places includes a computer-animated segment in which the camera seems to fly through the solar system. Space looks great in digital: those stars really pop against the newly-blackened background. After Greatest Places, we saw a segment of the new A Beautiful Planet — an IMAX film showing Earth as seen from the International Space Station. A sequence showing the lights of Earth at night (above) was dramatic in digital in a way it couldn’t be on film.

Of course, as with non-Omni movies, there will still be those who prefer the feeling of film — and for many of the same reasons. That’s one reason IMAX is encouraging SMM to keep its analog projector even after the digital system goes online. IMAX already has its auteurs who are fighting to preserve the original film format, but film has liabilities with respect to dome projection that it doesn’t have on flat screens, so filmmakers will have to weigh the pros and cons differently in the two cases.

While there’s no firm date set for the public debut of SMM’s new digital projection system — much work remains to be done, though it’s progressing quickly — the occasion will be something Omni buffs, and film aficionados generally, won’t want to miss. (In what might count as this story’s buried lead, the digital projectors will also give SMM the ability — at least theoretically — to show films in 3D.) Seeing a sharper, deeper, digital picture on a dome screen will be an experience you’ll be able to have, for a while at least, only in Minnesota.

– Jay Gabler