Fred Archer was a photographer best known as the co-inventor of the zone system along with Ansel Adams, circa 1939-1940. The zone system is a technique that allows photographers to translate light into specific densities on negatives and paper, giving better control over finished photographs. While the zone system is often credited to Adams, Adams always credited Archer as a co-equal in its creation. Wikipedia
The definitive Wikipedia entry for Fred Archer. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Fred_Archer_%28photographer%29