When Eastman Kodak introduced 35mm Tri-X back in 1954, it quickly became the go-to black-and-white film among photojournalists. With its wide latitude—it could be shot at ISOs ranging from 50 all the way up to 3200—Tri-X could handle nearly any situation, from war zones to the urban jungle. Don McCullin’s iconic image of a shell-shocked US soldier in Vietnam? Tri-X. Sebastião Salgado’s hellish vision of Brazilian gold mines? Tri-X. The film represents photography’s raw underbelly, and it stamps its unmistakably gritty authority on everything it records. The visceral physicality of its translation of light into silver is something that can be mimicked, but not matched, with digital technology. Though Tri-X has gone through a number of manufacturing permutations over the decades, the film’s character—its versatility and distinctive grainy quality—remains unchanged. It continues to be widely used today, and with luck it will continue to document our world well into the 21st century.