Ansel Easton Adams (February 20, 1902 – April 22, 1984) was an American photographer and environmentalist. His black-and-white landscape photographs of the American West, especially Yosemite National Park, have been widely reproduced on calendars, posters, and books. With Fred Archer, Adams developed the Zone System as a way to determine proper exposure and adjust the contrast of the final print. The resulting clarity and depth characterized his photographs. Adams primarily used large-format cameras because their high resolution helped ensure sharpness in his images. Adams founded the photography group known as Group f/64 along with fellow photographers Willard Van Dyke and Edward Weston.