Work on the Science Museum of Minnesota's multimillion-dollar conversion of its Omnitheater to digital ended in October, but there was still one step left: unveiling the movie that the museum helped to produce to show off the new technology.

And show it off "Ancient Caves" does.

The new digital cameras can go places and do things that their film predecessors never could. It's hard to conceive that a movie shown on a 90-foot-tall screen can seem claustrophobic at times, but this journey hundreds of feet deep into underground passageways manages that, thanks to a smaller camera that can squeeze through tiny crevices.

"The camera is about the size of a shoe box," said Mike Day. A longtime leader of the giant-screen movement, Day recently retired as the museum's executive vice president but still chairs the group that produced the film. "The old cameras were about the size of a lawn mower — and just as noisy.

"For the first time, we were able to mic the people on the scene [rather than record voice-over narration later], so we're actually hearing what they're saying to each other. We're getting their real commentary. We're getting more authenticity."

As for the quality of the photography, even Day admits that he's surprised by it. When filming started, he recorded a 17-shot sequence both digitally and on 70-millimeter film. Then he screened the footage and asked a test audience if they could determine which was which.

"These were all movie people," he said. "No one got it right."

Most of the caves in the movie are flooded, so the bulk of the footage of them is underwater. (Did we mention claustrophobia?) And not just a little underwater; some filming was done as much as 300 feet below the water's surface.

What the scientists are looking for is, in effect, a chronology of Earth. The layers of sediment that form stalagmites and stalactites "are similar to tree rings," Gina Moseley, a paleoclimatologist (a person who studies past climates) at the University of Innsbruck, explains in the film. But while trees have limited life spans, stalagmites offer "millions of years of data."

Core samples are sent to Larry Edwards, a geochemist at the University of Minnesota. Using a uranium dating technique he's been developing for 30 years, his lab can pinpoint the era of each layer of sentiment to create a climate history.

"The layers are basically time capsules," he said.

The movie is narrated by Bryan Cranston of TV's "Breaking Bad" fame. But he has less to do than the narrators of previous Omnitheater documentaries because we get to hear the scientists talking among themselves.

The film was produced by the Giant Dome Theater Consortium, a group of science museums. Through Day, the consortium approached Edwards in 2016 with the idea for the movie, and he directed them to Moseley, with whom he often works.

"I don't go into caves myself," Edwards chuckled. "I rely on other people for that."

In addition to the lighter camera — which for several shots was attached to a drone that was flown through the caves, producing some amazing sequences — going digital allowed the shooting of much more footage than the expensive-to-develop film.

"That's both a blessing and a curse," Day said. It made editing harder than usual because they had so many more good shots to pick from.

One of the advantages is yet to be seen. Because the editing is done on computers and the movie is shown via another computer, the process doesn't involve the striking of a print. Things can be changed quickly.

"If the need arises, we can update the movies easily," Day said. In fact, they were still tweaking "Ancient Caves" on the Sunday before it debuted.

As for what lies ahead, Day isn't sure. Because it was all new technology, everybody was starting at square one, "learning as much about the format and the experience as they could."

If "Ancient Caves" is any indication, the future holds fascinating possibilities.