In this study for a larger painting (see below), Bridget Riley explores subtle color variations and rotating oval forms that cause viewers to question which colors are in front of the other. This is a classic element of Op (optical) Art, in which movement and vibration are conveyed through geometric patterns and contrasts of color. Drawings are often the first step in the process toward a finished work and, as such, are a direct reflection of the artist’s intention. Here, Riley is working out a pattern that will become an exacting painting, but in this study, she is not concerned with absolute precision. The brushstrokes visible at the edges of the composition give viewersa sense of the hand of the artist—often less visible in the final work—and one of the ways drawings can reveal a lot about artistic process.