There are two options for wireless communication built into the 600EX-RT Speedlite system: radio OR optical. If you are using only 600EX-RTs as slaves, then take advantage of the radio system. The range is longer than optical wireless and you won’t have to worry about the signal being blocked by opaque surfaces. If you are using the 600EX-RT with earlier Canon Speedlites (500- and 400-series Speedlites), then you must operate the 600EX-RT in optical wireless (either as a master or a slave).
Notice that I said radio OR optical. It is not possible to send instructions to a 600EX-RT via radio and then have it optically transmit those instructions to 500- and 400-series Speedlites. That would be radio AND optical. Pick one wireless mode OR the other. If you want to use a 600EX-RT with non-radio Speedlites, then the 600EX-RT must be in Optical Wireless.
Setting Up the 600EX-RT Speedlite as a Radio Slave—Four Steps
There are four steps to using a 600EX-RT Speedlite as a radio slave. Think A-C-I-G and you’ll remember them.
- Activate the 600EX-RT as a radio slave
- Set the Channel of all slaves to match the master (Auto or Channels 1-15)
- Set the Wireless ID of all slaves to match the master (0000 to 9999)
- Assign each slave to a Group (five options A-E)
Step 1. Activate Each Speedlite as a Radio Slave
- Find the Wireless Mode Button. It’s on the left side of the Speedlite. Look for the sideways flashbolt, which is Canon’s symbol for wireless flash.
- Press the Wireless Mode button repeatedly. The unit will cycle Solo > Radio Master > Radio Slave > Optical Master > Optical Slave > Solo. [Bonus tip 1: if you only shoot radio wireless or only optical wireless, use Personal Function 06 to deactivate the wireless mode that you don't use. This way you can't accidentally activate a 600EX-RT in the wireless mode that you never use.]
- Look for the word Slave appear on the LCD. [Bonus Tip 2: Use Personal Functions 02-04 to specify whether the color of the LCD is orange or green in solo, master, and slave modes. I use green for solo and master and orange for slave.]
- Look for the radio wireless icon in the upper right corner of the LCD. This icon tells you Radio or Optical.
Step 2. Set the Channel of All Slaves to Match the Master
- The factory default channel is AUTO. In radio wireless, the 600EX-RT has 15 channels. If the Master is in AUTO, then the Slaves must be in AUTO. If the Master is set to a specific channel (1-15), then the Slaves must be set to that same channel. Industrial and corporate settings may have wireless devices that are using the same 2.4 Ghz channels used by the 600EX-RT. So, switching channels may extend the range at a particular location. (In another post, I’ll cover how to use the channel scanner that is built into the 600EX-RT and ST-E3-RT systems.)
- Look at the Channel ID—The channel ID appears on the LCD just below the Radio/Optical icon in the upper right corner. Again, like a walkie-talkie, the channel on the master and the slave(s) must be the same.
- Head to Menu 3. Tap-tap-tap on the Menu button (rightmost of the four interactive buttons) until you see Menu 3 appear above the button
- To set the Channel
- press the CH button
- turn the Select wheel until you get to the desired channel (AUTO is one click to the left of Channel 1)
- press the Set button in the center of the Select wheel to confirm your selection
Step 3. Set the Wireless ID Code of All Slaves to Match the Master
- Set the Wireless ID Code. In addition to the channel, you must also specify a Wireless ID Code on your 600EX-RTs (and the ST-E3-RT Transmitter, if you have one). The factory default code is 0000. The purpose of the Wireless ID is to allow multiple Speedliters (literally up to 10,000) to use the same radio channel.
- To set the Wireless ID Code:
- press the ID button (immediately right of the CH button on Menu 3)
- turn the Select Wheel until the digit you want to change is underlined
- press the Set button at the center of the Select Wheel (the number will backlight on the LCD, as shown above)
- turn the Select Wheel to change to the desired digit
- press the Set button to confirm your selection
- turn the Select Wheel again so that the next digit you want to change is underlined
- repeat the above steps until all the digits have been changed as needed
- when you have the desired code set, press the Return button (the rightmost of the four interactive buttons, look for the U-turn symbol above). Now you’re back at Menu 3.
- Check that the Link Light is green. When the Channel and Wireless ID settings are correct between master and slave, the Link Lights will glow green.
- If a Link Light is red, check the following:
- master Speedlite is turned on and set as a Radio Master
- slave Speedlite is turned on and set as a Radio Slave
- Channel setting on the slave matches that on the master
- Wireless ID setting on the slave matches that on the master
Step 4. Assign Each Slave to a Group
- Assigning slaves to different Groups gives you the ability to operate those Speedlites at different power settings. In Canonlandia, the master Speedlite is always a member of Group A. So, there is no option to set the Group on a Master. If you have a two-light shoot with the Master Enabled (which I wrote about here), then assign your slave Speedlite to a Group other than A so that you can control its power independently of the master’s power setting. (If you are shooting in ETTL with ratios, then the slave should be in Group B.)
- There are five Groups (A–E) in Canon’s radio wireless system. Assign all the Speedlites doing the same job to the same Group. For instance, when I use multiple Speedlites inside an Apollo softbox, all of those units are assigned to the same Group.
- To change the Group assignment on a slaved 600EX-RT, head to Menu 1 and look for the Gr icon. Tap-tap-tap on the Gr button until the desired Group ID appears in the box on the left side of the screen.
A Quick Word About the New Group Mode
- Canon now uses the word Group in two ways. The traditional way, as discussed above, deals with the assignment of slaves to specific groups so that they can fire at different power levels. The second usage, introduced with the 600EX-RT, refers to a new Speedlite Mode (joining ETTL, Manual, Multi, and External).
- If you have a 2012 or newer camera model (1D X, 5D Mark III, 6D, T4i/650D, EOS M) you can shoot radio wireless in Group Mode—which gives you the ability to turn individual groups on/off and to assign the mode of each group independently (meaning you can have slaves in ETTL, Manual, and/or External Auto all at the same time).
- If you have a pre-2012 camera model, the Group Mode settings appear to operate on the LCD of the 600EX-RT master Speedlite and the ST-E3-RT transmitter, but…when you fire the camera the Speedlite mode defaults back to ETTL and all of the the flashes fire at the same power level. This is due to the fact that pre-2012 cameras do not know about radio.
Changing the Mode and Power of Slave Canon Speedlites
The master is the place you change the mode and power setting of your slaved Speedlites. Read that sentence repeatedly until the message sinks in. Once you’ve gone through the four-step A-C-I-G checklist to set up your slave Speedlites, you control their mode and power settings via the master (either a 600EX-RT or the ST-E3-RT Transmitter).
You won’t see the change on the slaves until you press the shutter button. The changes are transmitted from the master to the slaves the next time you press the shutter button. Then, in an instant, the slaves change their settings as instructed and fire at the proper moment.
This is the great advantage of using the wireless system built into your Canon gear. You have full control from the convenience of your camera LCD (if you don’t know how to do this, read this post on accessing the Speedlite menu on your camera). If you want to run your slaves in Manual, tap the Mode button on the Master and dial the power in directly. If you decide that ETTL is better for the specifics of the shoot, then tap the Mode button on the Master again and use Flash Exposure Compensation to fine-tune the power setting of the slaves. (PocketWizards and other types of radio triggers break this on-camera control, which is why I seldom use them with Speedlites.)
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