Sigmar Polke, "Photocopierarbeiten"

In the early 1990s, when Sigmar Polke began using a copier, Photoshop was only a few years old and confined to commercial-design firms. Yet in these black-and-white images dating from that period, Polke managed to create exaggerated, Photoshop-filter-like effects by dragging halftone images and old engravings across a Xerox machine's scanning bed—a technique that resulted in scores of images that pushed his long-term fascination with Ben-Day dots in a hallucinogenic direction.