Canon Speedlite 420EX Instruction Manual page 24

Flash in Other Picture-Taking Modes
: E-TTL Autoflash and Manual Exposure
When you want to set both the shutter speed and aperture, use manual
exposure. E-TTL autoflash controls the flash output according to the
aperture you set. The background exposure is determined by the shutter
speed and aperture combination.
24
1 Set the camera's Command Dial
to < >.
• Set the high-speed sync switch to
< >.
2 Set the desired aperture and
shutter speed.
• Turn the camera's electronic dial.
• Set shutter speed anywhere from 30
sec. to the camera's fastest sync
speed.
3 Take the picture.
• Focus the subject, check that the
< > icon is lit in the viewfinder, then
take the picture.