Canon 600EX-RT Instruction Manual page 39

.: Manual External Flash Metering
You can manually set the Speedlite with the ISO speed and aperture set
in the camera. The flash output is automatically adjusted according to
the ISO speed and aperture that you set.
You can check the effective flash range on the Speedlite's LCD panel.
When using manual external flash metering and shooting with the camera
and Speedlite's PC terminal connected by a commercially-available sync
cord, you can shoot with the flash off the camera.
If you connect a different Speedlite to the Speedlite's PC terminal with a
sync cord, it will not fire.
//.: Flash External Metering
1
Set the flash mode to <.>.
Press the <E> button and set to
<.>.
If <.> is not displayed, set the
flash Custom Function to C.Fn-05-3
(p.96).
2
Set the same ISO speed as on the
camera.
Press function button 3 <I>.
The ISO speed value is highlighted.
Turn <9> to set the ISO speed, and
press the <8> button.
ISO speed can be set within a
maximum range of ISO 25 to 51200,
in 1/3 increments.
3
Set the same aperture as on the
camera.
Press function button 4 <D>.
The aperture is highlighted.
Turn <9> to set the aperture, and
press the <8> button.
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