the history of the single-lens reflex camera (slr) begins with the use of a reflex mirror in a camera obscura described in 1676, but it took a long time for the design to succeed for photographic cameras: the first patent was granted in 1861, and the first cameras were produced in 1884 but while elegantly simple in concept, they were very complex in practice. one by one these complexities were overcome as optical and mechanical technology advanced, and in the 1960s the slr camera became the preferred design for many high-end camera formats.