Canon SPEEDLITE 580EX II Manual De Instrucciones página 31

External Flash Metering
The flash reflected off the subject is metered by an external metering
sensor in real time. When the standard flash exposure is attained, the
flash output is cutoff automatically. Auto external metering compatible
with the EOS-1D Mark III and manual external metering compatible with
all EOS cameras are provided.
8: Auto External Metering
With auto external metering, the camera's ISO speed and aperture will
be set automatically in real-time by the Speedlite.
Auto external metering will also work with flash exposure compensation
(p.14) and FEB (p.15).
8q: Manual External Metering
30
Set auto external metering.
Set the Speedlite Custom Function to
C.Fn-05-2. (p.27)
Set manual external metering.
1
Set the Speedlite Custom Function to
C.Fn-05-3. (p.27)
Set the Speedlite to the camera's
2
ISO speed.
Press the <8> button so the ISO
speed blinks.
Turn the <9> dial to set the ISO
speed, then press the <8> button.