 The most significant one is perhaps the full aperture metering facility, allowing the exposure to be set accurately without stopping down.Full aperture TTL metering was commercially first realised in the 1963 Tokyo Kogaku Topcon RE Super.Another unique feature of the SR-T 101 besides the open aperture metering at the time of its release to the public at Photokina in 1966 was the so called "CLC"-metering characteristic.