The drawings beneath the surface of the 26 painted panels reveal a world hidden for half a millennium.

RANDY ELI GROTHE/DMN

Mark Roglán, director of SMU's Meadows Museum, and Claire Barry, chief conservator of the Kimbell Art Museum, were among several experts assembled to participate in the project.

Some contain inscriptions written in Old Castilian Spanish that specify what color paints were to be used. Others demonstrate changes in thinking about composition. All show the elegant draftsmanship of the two artists who painted the works, which were created near the end of the 15th century for the massive altarpiece of the Cathedral of Ciudad Rodrigo in northwest Spain.

Images of the underdrawings, as well as the panels themselves, are on display in an exhibition opening Sunday at Southern Methodist University's Meadows Museum, titled "Fernando Gallego and His Workshop: The Altarpiece From Ciudad Rodrigo." The exhibition marks the completion of a five-year analysis of the artworks that blended contemporary science with traditional art conservation and aims to educate the public about the forensic approach experts are increasingly using to shed new light on very old art.

"The scientific analysis performed on the panels has allowed us to step back 500 years," says Meadows director Mark Roglán, who led the initiative. "Seeing these underdrawings is like looking into the minds of the artists."

Mostly painted in the period from 1480 to 1488, the panels depict biblical scenes from Creation through the Last Judgment and were designed to fit onto a towering structure of gilded pine that sat behind the altar in the cathedral apse. The altarpiece may have held as many as 34 panels, but the missing works, as well as the altarpiece itself, have not survived the years.

Dr. Roglán first encountered the panels on a 2003 visit to the University of Arizona Museum of Art in Tucson, which owns the artworks. The panels had traveled a circuitous route after being disassembled in the 18th century and were given to the university by the Samuel H. Kress Foundation in 1957.

Dr. Roglán immediately raised the prospect of bringing them to North Texas for study. "It represented an absolutely unique opportunity, because it's astonishingly rare to have so many intact panels from a major altarpiece, especially here in the United States," he says.

Ultimately he assembled experts from the Meadows, the Kimbell Art Museum in Fort Worth, the Prado Museum in Madrid, Spain, the Getty Research Institute in Los Angeles and the Art Institute of Chicago to participate.

As the exhibition makes clear, the paintings – oil paint applied on pine panels – were created primarily by artists working in tandem. Fernando Gallego (active c. 1468-c. 1507) was the best known and most important artist in the city of Salamanca in the late 15th century. He, as well as members of his workshop, including his brother Francisco, have long gotten the lion's share of credit for the panels.

Almost nothing has been known about the second artist, once referred to as "The Master of Armor," but identified late in the 20th century as the Maestro Bartolomé (active c. 1480-c. 1500) based on comparison with a lone work signed by Bartolomé in the Prado. These days Bartolomé is considered responsible for a dozen of the panels, and the analysis revealed the first information about his working practices and fills out what's known about his influences.

"I think this lays the groundwork for a major enhancement of the artistic reputation of Maestro Bartolomé," says Claire Barry, chief curator of paintings at the Kimbell, who oversaw much of the scientific research and produced the underdrawings.

To coax out the sketches, she used a technology called infrared reflectography, which employs infrared light to penetrate painted surfaces. Each infrared photo showed a roughly 6-square-inch section of the underdrawing. Since most of the panels measure about 5 by 31/2 feet, reproducing an entire underdrawing required as many as 300 shots per panel. A computer software program assembled each final "mosaic."

The exhibition presents most of the panels dramatically arrayed along a semicircular red wall, while the images of the underdrawings are displayed in backlit "light boxes" in hallways on either side of the main room. The technological accomplishment that's meant to be highlighted is impressive, though the stars of the show are the luminous paintings themselves, whose style owes something to both Gothic idealism and Renaissance humanism.

The artworks are in beautiful condition, with the exception of a hole in one of the panels caused by an artillery shell fired by Wellington's army during the Peninsular War in the early 1800s.

Ms. Barry's study also provided conclusive evidence that a work in the Meadows permanent collection, Acacius and the 10,000 Martyrs on Mount Ararat, was painted by Francisco Gallego, not Fernando, as some experts believed.

The displays are accompanied by an exhibition of manuscripts and other works that influenced the creation of the altarpiece from SMU's Bridwell Library, as well as an installation about the science of forensic art analysis organized in collaboration with the Museum of Nature and Science.

Kevin Richardson is a Dallas freelance writer.

PLAN YOUR LIFE Opens Sunday and continues through July 27 at the Meadows Museum at Southern Methodist University, 5900 Bishop Blvd. Companion exhibition "Apocalypse: Images From the Book of Revelation" is on view through June 22. Hours: 10 a.m. to 5 p.m. Tuesdays, Wednesdays, Fridays, Saturdays; 10 a.m. to 8 p.m. Thursdays; noon to 5 p.m. Sundays. $8, free each Thursday after 5 p.m. 214-768-2516, www.meadowsmuseum dallas.org.