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

(L-R) 600EX-RT Wireless Mode button, Slave & Master icons, Radio Wireless icon, Optical Wireless icon

    • 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

Channel and Wireless ID settings are made on the Menu 3 screen of the 600EX-RT

    • 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

Wireless ID Code set-up on the 600EX-RT

    • 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.

Left: red Link Light indicates that master and slave are not communicating. Right: green Link Light indicates that master and slave are working together.

    • 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

The Group icon and Group button on the 600EX-RT.

    • 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

Group Mode in Radio Wireless enables the use of different modes at the same time. Group Mode also allows you to turn groups on/off individually.

    • 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

To change the mode and power of a slave Speedlite, use the Mode and Power buttons on the master. Shown here: the ST-E3-RT Transmitter.

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.)

600EX-RT Speedlite Current price on Amazon • Current price on B&H

ST-E3-RT Speedlite Transmitter Current price on AmazonCurrent price on B&H
 

27 Responses to Controlling Canon Speedlites as Slaves—Part One: 600EX-RT as Radio Slave

  1. Great stuff as always Syl, I’m loving the 600 EX-RT, I use 3 controlled via a ST-E3. It’s a wonderful system that’s a pleasure to use.

  2. Tony Dunn says:

    Thanks, Syl. I wish I’d seen this post a week ago. I just bought 3 600EXs and the ST-E3 and spent the better part of an hour trying to figure out what your post explained in 5 minutes.

  3. Can the settings be saved. In other words, if I use three 600ex flashes to shoot a home (I am a real estate photographer) and pack up, go to the next property. Do I need to re-sync or does it save my settings so I can in pack and start shooting?
    Thanks!

  4. [...] • Part One: 600EX-RT as Radio Slave • Part Two: Fundamentals of Optical Wireless (this part) • Part Three: Setting Up Speedlites as Optical Slaves (coming) [Note: In this series, I am writing about the master/slave system built into Canon Speedlites. There is another type of optical slave that is common in studio lighting. It fires the strobe when it senses a flash of bright light, but all changes to power, sync, etc. must be made manually on the unit.] [...]

  5. Brian says:

    Hi,

    I cannot get the option of assigning my 600EX as slave during radio Tx. Please help

  6. Giovani R Pop says:

    I have a 7d purchased in 2010 and a 5d mark II purchased in 2012. I also have 3 580ex II. Should i switch to the 600ex or not? Money is not a issue. Could I have full control with these two cameras or not? What would you recommend? Thank you! Gio

  7. [...] Arena has mentioned this in his on-line instructions covering these new radio controlled units! (Part 1 and Part 2) This allowed me to meter the flash power outputs just like you normally would with [...]

  8. Repsac says:

    How easy is it to switch on/off the slave groups?
    E.g. when shooting in the direction of your own slave, you may want to quickly turn it’s group off.

    • Syl Arena says:

      With the 600EX-RT and a 2012 or newer camera model, you can use Group Mode — which enables you to turn specific groups on /off. With earlier Speedlites / cameras, the most you can do is dial the power down in Manual to 1/128 for the group that you want to minimize.

  9. Mobius Strip says:

    Thanks for this post, Syl. A question:

    I’m using a 5D Mk II and one on-camera 600EX (master, obviously)and one off-camera 600EX (slave). Connection is radio wireless.

    Q: What’s the difference between setting the Master to ‘ALL’ and using flash exposure compensation to control power, and setting the Master to ‘RATIO’ and controlling power right from the Master?

    Thanks.

    • Syl Arena says:

      ALL fires all the slaves groups at the same power level. RATIO allows the individual slave groups (A,B,C…plus D & E on the 600EX-RT) to be adjusted in relation to each other. Flash Exposure Compensation (FEC) will apply to the entire system. So, you can apply FEC to ratio-controlled slaves. In the case of having one off-camera light, ALL + FEC is the simplest way to go.

  10. Syl, I’m still confused with using two 600exrts with a 5DM2. If I have one on my M2 and one setup remotely, can I use these in radio mode? More importantly can the master that is on the M2 remotely control the power on the other one?

    Thanx.

    • Syl Arena says:

      The only limitation with using the 5DM2 and the 600EX-RTs is that you have to control the system via the LCD on the master Speedlite (rather than via the LCD on the newer generation of cameras, such as the 5DM3). Yes, the Canon wireless system allows you to control the power of slaved Speedlites via the master.

  11. Sergio Fialho says:

    Dear Syl,
    I just bought a 600ex-rt and a 70d. Is it possible to use the built-in flash of the camera to trigger the speedlite?
    Could you give me some advise?
    Thanks from Brasil!

    • Syl Arena says:

      @Sergio -

      The 70D is happy to control a 600EX-RT via the pop-up flash. Make sure that your Speedlite is set to Optical Wireless. Also, turn the body so that the red panel on the front is facing the camera. The optical slave sensor is just above the red panel. Then turn the head of the flash back to your subject.

  12. prasad menon says:

    in GR setting, 600ex rt flash in slave and ettl mode, st-e3-rt doesn’t transmit FEC to the flash though the flash fires(correct matching group, channel and mode)
    many thanks.
    Prasad

  13. Larry B says:

    How to set ST-E3-RT as master & 600 EX-RT as slave using High Speed Sync. Camera is 5D Markiii I cannot find the settings. High Speed Sync on the 600 EX-RT but not on the ST-E3-RT

  14. Frank Weber says:

    I have a 1d mark IV and would like to use 600exrt on camera, ETTL and a 600exrt slaved in manual mode. I do not want to adjust the slave, just have it in manual. IS the pre 2012 camera getting in my way….

    I have the Calumet QUAD plus that I have used with my 580′s I can drop the 600′s on them.
    Thank you!!!

  15. Ravi says:

    Great article. Thanks so much for putting this up (and answering questions.) :)

    I have a 6D and think I want to buy a few 600EX-RT’s. Would I also need a ST-E3-RT on the camera or does the 6D not need a transmitter?

    Thanks again!

    • Syl Arena says:

      @Ravi – If you want to control the 600EX-RTs via radio, you will need either a 600EX-RT Speedlite or the ST-E3-RT Transmitter in the hotshoe of your 6D.

  16. Stu Nowlin says:

    Syl,
    Your observations are real time savers! Thanks! I have 4 600EX-RTs controlled by my ST-E3-RT and mostly use Group settings. I just got 2 Profoto B1 units and the Air TTL Remote to use studio flash (500WS) and ETTL-II. It also works as advertised. I would like to use the Air TTL Remote on camera to control the B1s and optically trigger a couple of 600s as accent / hair lights via the B1′s flash output. Can this be done using the B1′s flash as a trigger?

  17. Stu Nowlin says:

    Syl,
    The Canon white paper on optical states that you can only use the ST-E2 to control the 600EX-RT unit in optical mode. I tested this and found that the optical setting (the thunderbolt) with the 600s only allows ETTL, not manual or any other setting. That is, it only recognizes signals from a Canon device and from no other. That is unacceptable. I can use my ST-E3-RT and Canon lights and also use my Profoto B1 stobes in optical manual mode and get the Profotos to fire. Further, I can control the Profoto units with the Air TTL-C remote OFF CAMERA to control light output. Canon does not allow this. What it means is that I will spend more money for Profoto units rather than Canon equipment. Stu

    • Syl Arena says:

      Stu – I’m not familiar with the white paper you referenced. 600EX-RTs can be controlled in optical wireless by many different optical masters: 600EX-RT, 580EX II, 580EX, 550EX, and the Macro Twin- and Ringlites. Manual mode is available on all of these optical masters. Keep in mind that, even in Manual mode, there is a pre-flash sequence prior to the shutter opening. This pre-flash is not ETTL. Rather, it is how the optical master communicates with the slave Speedlites. The pre-flash is the optical transmission of the instructions to the slaves. That said, I think the combination of the ST-E3-RT with a 600EX-RT as a radio slave is a great combination with studio strobes. For an all-Profoto system, the Air controller is a great solution.

      • Stu Nowlin says:

        Syl,
        Thanks for the reply! The paper is on the Canon Digital Learning Center, “QuickGuide to Speedlite 600EX-RT Optical Wireless Flash Setup”. It confirms what you said about using other Canon flash units and the ST-E2 to trigger the 600s optically. That is not my desire. I want to fire the 600s in slave mode in manual. I want accent / hair lights along with studio strobes. This is not possible with the 600s. Slave mode (thunderbolt symbol active) only allows ETTL, or another Canon device to trigger them. There is no manual mode that would allow the optical sensor to sense any other flash and fire. You do not need a pre-flash in manual. You do need a light meter. And then just set the power level as needed (1/64th, 1/32, etc.). The PocketWizard AC3 works this way in manual. Just set the power level and test it. Then shoot.
        Stu

        • Syl Arena says:

          Stu -

          What you are looking for as a way to fire a Canon Speedlite with an optical slave eye, such as the ones built into studio strobes. Canon does not include this circuit/sensor in their Speedlites. They can be added on externally. Just be sure that you get an adapter that is made specifically for Canon Speedlites.

          • Stu Nowlin says:

            Syl,
            Again I am indebted to you! I have been playing with Profoto B1 units that are ETTL-II capable. They are fabulous. You can do a test shot with ETTL-II, then switch to manual mode which preserves these ETTL-II settings and re-set groups A, B or C as needed in manual. Then shoot all of the, say, alter shots with this setting so that when the bride turns the white dress reflectance does not throw off the exposure. I have been using Groups with my speedlites with similar results. In my opinion the Groups setting is the preferred way to work. You can turn off any group(s) and see what the light contribution is and go from there. I love it.
            I will try to find a Canon specific sensor for my 600s that will allow me to use them in manual with my B1s (but obviously not in ETTL-II since the pre-flash would fire my 600s too soon.)

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