	The Nikon F, was delivered since 1962 with various pentaprism metering heads. The Photomic series of prisms, which was initially designed with a direct coupled-metering CdS photocell (2 models were produced). The Photomic prism head later evolved to include the Photomic T with TTL in 1965, a behind-the-lens metering prism head which metered an averaging pattern of the focusing screen. The later center-area reading Photomic Tn, concentrated 60% of its sensitivity in the central portion of the focusing screen and the remaining 40% for the outlying screen area. The Photomic FTn was the last of the Photomic finders for the Nikon F.