My Canon 580EX II has a distance scale running from 0.5m to 18m.
When the flash is in manual mode, a single segment of the distance scale illuminates to indicate the maximum effective range for my current aperture and ISO settings.
In E-TTL II mode, the scale illuminates a number of segments. For example, if I set my aperture to f5.6 and ISO to 400, 7 segments illuminate between 1m and 9m. What does this mean?