In the early to mid-twentieth century, Pyro found its most famous advocates. Ansel Adams, Edward Weston, and other Zone System pioneers relied on Pyro for its long tonal curve and ability to handle extreme contrast scenes. Adams’ negatives from Yosemite, printed decades later, still exhibit the smooth highlight roll-off typical of Pyrogallol development. Pyro allowed these photographers to “place” tones with mathematical precision — the foundation of the Zone System itself.