Through-the-lens spot metering was one of the groundbreaking new features offered by the Leicaflex SL, manufactured from 1968 to 1974.
In contrast to its predecessor (the original 1965 Leicaflex), the Leicaflex SL offered an internal, through-the-lens metering system capable of spot metering – as indicated by the initials SL, which stand for 'selective light'.
This metering method, which was revolutionary at the time, depended on the lens having not one, but two sloping cams – meaning that the lenses offered for the original Leicaflex had to be redesigned.
The Leicaflex SL was available in a chrome or black chrome finish, though a small number of black-lacquered models were also produced. In total, Leitz manufactured around 70,000 models of the Leicaflex SL.