Jacopo Tintoretto's "The Deposition of Christ," is nearly 10-feet long. (Gallerie dell'Accademia, Venice/Gallerie dell'Accademia, Venice)

With his high-concept, action-packed canvases, Jacopo Tintoretto was perhaps the Steven Spielberg of late Renaissance painters, says Frederick Ilchman, co-curator of “Tintoretto: Artist of Renaissance Venice,” which opens Sunday at the National Gallery of Art.

“His are really vigorous paintings with a lot of tumult and energy and surprise in them,” says Ilchman, a curator at the Museum of Fine Arts, Boston.

Well known during his lifetime, Tintoretto has been somewhat forgotten since — probably because his paintings tended to be enormous and nearly impossible to move, says the exhibit’s other curator, Robert Echols, an independent scholar.

In celebration of Tintoretto’s 500th birthday, many of his greatest works have undergone extensive restoration and will be traveling to America for the first time for this show.

“We hope this exhibit will give Tintoretto the high profile he deserves with the general public,” Echols says. Here, these Tintoretto experts explain what’s going on in a typically dense tableau, “The Origin of the Milky Way.”

1. The circa 1575 painting depicts a myth about the creation of our galaxy that the ancient Romans adapted from the ancient Greeks. The god Jupiter, flying in on the upper right, wanted to give his half-human son Hercules the gift of immortality, which could only be conferred by the breast milk of a goddess. So, while his wife Juno was sleeping, Jupiter placed baby Hercules on her breast. Juno woke up and flung the baby off of her. In the commotion, the milk she sprayed toward the heavens became the Milky Way. “Unlike Tintoretto’s serious religious paintings, this one is humorous and joyful,” Ilchman says. “Jupiter — what an idiot. He thought he could do this to his wife and get away with it.”

2. To impress the international client who commissioned this painting — probably Holy Roman Emperor Rudolf II — Tintoretto used expensive, vivid pigments, such as lapis lazuli for Juno’s blue blanket, Echols says. He also may have chosen the subject matter to flatter the painting’s viewers, Echols notes. “Tintoretto made this for a well-educated audience that was sophisticated about mythology, so the painting is full of abstruse references for them to get,” he says.

3. Ancient worshippers believed the eagle served as Jupiter’s personal messenger, and this one is carrying thunderbolts, the god’s weapon of choice, Echols says. “The peacocks are there because they are Juno’s sacred animal,” he adds.

4. The bottom third of the painting was cut off at some point, Ilchman says. “What’s missing, which we can see in an early copy, is a figure of Mother Earth with white lilies sprouting from her fingers and limbs” — flowers that were seeded by the droplets of Juno’s milk that sprayed down, Ilchman says. Poking up in the lower-right corner are fragments of foliage from the missing section of the painting. “It’s possible that someone in the royal household simply wanted a smaller painting, or wanted to fit it into a particular frame,” Ilchman says. What’s left is about 5 1/2 feet by 5 feet — a medium-size painting for Tintoretto.