PhotoNotes.org Dictionary - E-TTL

PhotoNotes.org Dictionary - E-TTL: "E-TTL.

(Canon) Evaluative through-the-lens flash metering, an EOS-specific flash metering technology.

E-TTL works by issuing a white light preflash from the main tube. This preflash illuminates the scene with a known flash level. The camera’s standard evaluative metering system then meters the flash pulse and sets the flash output accordingly. It does this prior to the shutter opening. E-TTL metering was enhanced in 2004 with the introduction of E-TTL II.

cf. A-TTL, EOS, E-TTL II, evaluative metering, preflash, TTL, type A camera.

Entry last updated 2004-02-11. Term 426 of 1486."

E-TTL II.

(Canon) Evaluative through-the-lens flash metering II, an EOS-specific flash metering technology introduced in 2004.

E-TTL II is an enhancement to regular E-TTL flash metering. It adds two basic functions.

First, flash metering patterns are dispensed with and the camera instead examines all evaluative metering zones both before and after the E-TTL preflash is emitted. It then discards or biases out any metering zones with excessively bright measurements during the preflash. This minimizes the risk of highly reflective surfaces throwing off the flash metering.

Second, it incorporates distance data from compatible lenses when appropriate, much like Nikon’s flash metering technology. This data assists the camera in determining correct flash output for the range in question.