Stephen Sheldon’s not an artist—he’s a professor of pediatrics and neurology at Northwestern. But a few years ago he joined his wife, Rebecca, on a series of studio tours as part of the Art Institute’s City Associates program. After a few visits he realized he was less interested in the artists’ work than he was in their tools, particularly their palettes.

Painters, he found, use a wide variety of materials for their palettes: milk cartons, paper bowls, pieces of glass, even tuna fish cans. “Their personalities are on the palettes,” Sheldon explains. Each painter uses his or her palette in a different way.

For example, most of the artists Sheldon shadowed weren’t aware they took “practice strokes.”

“It’s like the wiggle of a baseball bat or a golf club before you take a hit,” he says.

The neurological implications of those movements fascinated him. “The image is in the brain first,” Sheldon explains. “The muscle memory exists in the artist, and it brings out the vision, and it’s particular to each artist.”

One day over lunch he asked to photograph artist David Klamen’s palette. Now Sheldon is an artist too. “La Palette,” a show of his photos, opens next week at the Ed Paschke Art Center. The exhibition includes photos of 17 artists’ palettes, including Paschke’s. (He used sponges.)

“Ed said you can tell a true artist by his palette,” Sheldon says. “How they pick paint up is different from an amateur. And believe me, I’ve tried it.”

9/19-11/29, Ed Paschke Art Center, 5415 W. Higgins, 312-533-4911, edpaschkeartcenter.org, free.