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Overview: The Canon ST-E3-RT is a camera-mounted transmitter for
wirelessly controlling multiple Canon Speedlite flash units. The transmitter
uses 2-way radio waves to communicate between the master and slave units. It can
control up to 5 groups, or up to 15 individual flash units. It can be mounted to
Canon EOS digital cameras with a hot shoe. Some restrictions exist with cameras
released before 2012.
Range: The ST-E3-RT operates on 2.4 GHz radio frequencies which
provides 360° of coverage with a range of up to 30 meters (98.4 feet). Using radio waves, the unit
does not have the same directional limitations of traditional optical wireless
transmitters, such as physical obstacles.
Compatibility: The ST-E3-RT is compatible with Canon Speedlites with
the Radio Transmission Wireless Function, such as the
600EX-RT. It does not have an optical transmission function, so it is not
compatible with some earlier Speedlite models, such as the 430EX II or 580EX II.
Wireless Flash Shooting: Using a transmitter and a compatible Canon
Speedlite, you can shoot with advanced wireless multiple flash lighting in the
same way as using normal E-TTL II/E-TTL autoflash shooting. If desired, you can
also shoot in the Manual Flash mode. The settings of the transmitter attached to
the camera (master) are automatically transferred to the wirelessly controlled
Speedlite (slave). You can use one slave unit, or divide the slave units into
two or three groups, and perform E-TTL II/E-TTL autoflash shooting. You can also
set and shoot with a different flash mode for each firing group, up to five
Stroboscopic Flash: Stroboscopic flash is an advanced manual flash
shooting method with multiple flashes in rapid succession for a single photo.
Using stroboscopic flash with a slow shutter speed lets you capture successive
movements within a single picture, similar to stop-motion pictures. You can set
the number of flashes (up to 100) and the flash frequency (up to 500 Hz) in the menu. You will also need to
calculate the shutter speed (Number of flashes ÷ Flash frequency) to make sure the shutter stays open until the end of the
Modeling Flash: When the camera's depth-of-field preview button is
pressed, the flash fires continuously for 1 second. This "modeling flash" lets
you see the shadow effects of the flash on the subject and the lighting balance.
FEB: The ST-E3-RT's Flash Exposure Bracketing (FEB) function
allows you to take three shots while automatically changing the flash output.
The range can be set to up to +/-3 stops in 1/3-stop increments.
Linked Shooting: Linked shooting is a function that automatically
releases the shutter of a slave unit camera by linking it to a master unit
camera. You can shoot with linked shooting for up to 16 units, including both
master and slave units. This allows you to shoot a subject from multiple angles
at the same time.
LCD: The ST-E3-RT features a 1-7/8" (W) x 1-3/16" (H) LCD
screen that displays the flash transmitter's settings and status.
Transmission Channels: To avoid interference with wireless multiple
flash systems using radio transmission used by other photographers, you can
change the transmission channel (1 to 15 or Auto) and wireless radio ID (4-digit
number: 0000 to 9999). You should set the same channel and ID for both the master unit and the
Memory Function: You can save the wireless settings and recall them
for later use.
Power Requirements: The ST-E3-RT operates on two AA alkaline batteries
(not included). Fully charged batteries provide approximately 10 hours of
wireless flash shooting time. The unit will power off after 5 minutes of
inactivity to save battery power.