E-TTL
Short for Evaluative Through-the-Lens Mode. By Canon developed method for flash exposure measurement and -control. Contrary to TTL-flash control and -measurement, these two separate measure cells (one for the flash light and one for the ambient light) presupposes, becomes with the E-TTL the flash light also through the objective, however through the same measure cell measured as for the ambient light.This makes a precise syntonizing possible between flashlight and ambient light. With E-TTL flash measurement and -control, direct before de main flash and before the real exposure fires an ultra short (for the human eye not visible) measuring pre-flash, which an adjusted and capable electronic in camera and flash becomes.Therefor the E-TTL system will only function with the corresponding Canon cameras and flashes.
