On page 1.) we established that TTL/BL uses the distance info from the lens "when the flash is facing forward" . Of course in most situations we want to avoid direct flash but outdoors where there is nothing to bounce off , and in bright sunlight where the flash isn't the main light source , we still use it sometimes .
Just a quick review of TTL/BL and the distance factor - first a properly focused picture ....
Then we manually go to close focus and the flash dims down automatically
and as we change the focus distance to 20 metres it brightens up ....
proving that the focus distance directly affects the flash .
Now for the proof in real life . I set up my model ''Stinky'' indoors to only show the flash with little ambient to detract from the results . I left a reflector in the same position and then moved the subject under the focus point further away . This is what TTL did with the scene - it was totally fooled by that white reflector and exposed for it the whole time .
Now on to TTL/BL . Even though the reflector was in the same position reflecting back a lot of light TTL/BL continued to meter for the active focus point on the subject and was not fooled by the white object in the frame .
This proves that TTL/BL is superior with direct flash photography - it's a pity it doesn't have that reliability with bounce flash and wireless CLS .
Of course it isn't a simple program and there may still be some surprises when we use it but I am slowly coming to grips with its 'logic' .
Using direct flash outdoors is not the problem , predicting results indoors where the flash is the main source of light is more of a challenge because there is little ambient light to hide our mistakes as with pictures in bright sunlight .