Tom Shea , Jan 04, 1998; 07:37 p.m.
Phil, E-TTL utilizes a pre-flash to measure the light reflected back from the subject. When the shutter is pressed, a very short burst is fired from the flash unit. The metering system reads the results and adjusts the "real" flash duration as it flashes a moment later. All of this takes a very short period of time and I cannot actually see the pre-flash or tell that it has happened because all of this happens so quickly.
The metering pattern is rather broad - center, left weighted or right weighted, depending on which of the focus points is used.
My experience with E-TTL has been very positive. However, like any system, one must understand what is going on and make the necessary adjustments. E-TTL does tend to overexpose portraits in my experinece, so I use the flash exposure compensation when I shoot portraits with it. Since the Elan IIe has flash exposure compensation separate from the overally exposure compensation control, you can set them separately. This provides great flexibility and control. But there is no magic - you have to pay attention and understand what is happening.
Actually, my main use for E-TTL is for macro photography. I have been extrememely pleased with the results for macro work.
If your want a similar system that uses a pre-flash and a spot meter, the Contax RTS III is the only camera that does this.