>Well, yes and no. I took test shots with TTL-BL and the >settings as above, but I downplayed the background a bit so >that the focus of attention is the subject. I will try some >back-to-back shots with TTL vs TTL-BL to see what happens. > >Again thanks!
The key to making TTL-BL work right is to make sure the camera light meter is zeroed (centered). You must have a correct ambient exposure for the system to add proper fill.
If you are indoors in low ambient conditions (like a night club), it is often very difficult to get a correct ambient exposure without slowing the shutter way down (and risking severe ghosting). This is one of the key reasons you should not try to use TTL-BL when in low ambient conditions.
Regular TTL does not measure ambient light and will fire at the samme power regardless of the brightness of the ambient light. This is why you have to turn regular TTL way down in order to use it in the daytime. However, in the dark ambient of a night club, regular TTL is exactly what you need. In this case, the flash is primary, meaning it will provide nearly all the exposure.