After doing my own research to work through the confusion of the change of Nikon TTL/BL from "back-lit " mode to "balanced fill flash " I published a blog on it called "Nikon's "new" TTL/BL" to help others understand how it works .
Due to the fact that Nikon had changed the system without really explaining much it has taken a while to convince many of those who thought they knew how it worked .
I recently decided to start reading up on Canon E-TTLii and found that it is almost the same system - so now many of you Canon users could probably learn about E-TTLii from my blog on TTL/BL !
While reading up on it [ I have not done my own tests but Canon seems to hand out the information more freely than Nikon !] the similarities are the fact that
1.) E-TTLii now uses distance information as does BL mode .
2.) E-TTLii now takes the ambient into account [ based on my understanding of the description of how it works ] so should need less exposure compensation when the ambient is correctly exposed
3.) E-TTLii can analyze a pattern and determine that a bright spot is a reflection based on its pre-flash reading compared to the ambient reading of the subject . I would imagine that Nikon has a slight advantage here with its greater number of metering segments - Nikon also advertises that TTL/BL is good for reflective surfaces and I am assuming that it is for a similar reason to the Canon description.
I see that E-TTL has also gone through a few changes but at least Canon changed the name accordingly and explained those changes .
Perhaps a diligent Canon user could duplicate some of my tests on my blog and confirm 1.) the change in exposure with a change in focus distance ...
2.) and then perhaps the most important test of all is the one to see if the flash output changes with a change in the meter reading .
Set the camera up on a tripod with a subject to the side . Set the metering mode to CW or pattern and find a point where the exposure registers a one stop difference between the two modes without changing any other settings . If E-TTLii changes its output based on a simple change in the position of the meter then it is the same as TTL/Bl mode .