Produced by KelbyOne

Canon Speedlite 600EX-RT & Speedlite Transmitter ST-E3-RT

New Flagship Flash and Transmitter Changes the Game

It's an exciting time for the Canon Speedlite community. Canon's new radio-enabled 600EX-RT Speedlite and companion ST-E3-RT radio transmitter are a quantum leap forward in wireless E-TTL handheld flash technology. It's a safe bet other handheld flash manufactures will soon follow suit.

Replacing the 580EX II in Canon's lineup as their flagship Speedlite, the 600EX-RT and ST-E3-RT both have built-in 2.4-GHz radio transmitters for wireless E-TTL and manual flash communication. The 600EX-RT also carries over wireless optical (IR) technology from the previous generation, making it fully backward compatible with the 580EX, 580EX II, 430EX, 430EX II, 320EX, and 270EX II, which are exclusively optical based. Wireless control must be either all optical or all radio, not a mixture of both.

Regarding compatibility, full access to the in-camera wireless external Speedlite menu controls requires a 2012 or later EOS camera model, such as the 5D Mark III or 1D X. This isn't a problem due to the much-improved, easier-to-navigate menu system on the 600EX-RT and ST-E3-RT. Contrary to Canon's published documentation, wireless high-speed sync does work up to 1/8000. on a 5D Mark II and 60D. Pre-2012 EOS model cameras will experience a 1-stop reduction in the maximum sync speed available for flash when using radio-enabled wireless E-TTL.

Optical triggers rely on unobstructed line-of-sight for successful communication between master and slave flashes, have a limited range of approximately 30′, and spotty performance in bright sunlight. Radio triggers have no such limitations: their signals pass easily through walls, doors, and windows, and can travel around corners and much longer distances. These features make radio communication significantly more reliable and desirable for wireless off-camera flash.

The 600EX-RT and ST-E3-RT have many new robust features, including 98′ of radio range, remote power control of up to 5 separate Speedlite groups or 15 individual Speedlites, 15 radio channels, and personal pin numbers for channels in multiple shooter/trigger environments. You can also mix Speedlites in both E-TTL and Manual modes, and remotely power on/off individual Speedlites (to easily see the affect of each light). A Link light confirms communication between the master and slave units, a ready light confirms all slaves are ready to fire, and you can perform remote camera firing.
In a stroke of usability genius, the engineers at Canon made the ST-E3-RT an almost exact duplicate of the 600EX-RT except for the missing flash. Once you've learned one piece of equipment you've learned them both.

The ST-E3-RT's lack of a built-in AF-Assist Beam like the one on the ST-E2 means photographers working in low-light situations will likely want an additional 600EX-RT to use on-camera for the built-in AF-Assist Beam.

Other significant improvements include:

  • Zoom: Increased range is now 20-200mm
  • LCD: 40% larger LCD with larger, more legible dot matrix text, and choice of green or orange background colors (useful for assigning different colors to master and slaves).
  • GUI: Combined with the LCD and buttons, this is a vastly improved user interface with straightforward menu navigation. Menu items no longer jump around but instead appear in the same places making them much easier to find. Custom functions now have easy-to-understand menu descriptions.
  • Buttons: New dedicated one-button access to wireless functions and a lock switch to help safeguard settings. Confusing multifunction buttons have been replaced with four function buttons, each with one use. Button functions change interactively depending on the mode or screen you're in. There's also a larger Mode button for accessing all five flash modes.
  • Build: Weather sealing to match 1D X, improved hot shoe contacts, and more rugged case.
  • Power: Increased GN (guide number) to 197′ (60m) at ISO 100.
  • Filters: Includes filters, filter holder, and case.

All things considered, these babies are a dream come true—albeit an expensive dream at $629 for the 600EX-RT and $329 (street price) for the ST-E3-RT transmitter. The good news is no additional equipment is needed for wireless E-TTL and manual radio communication between your Speedlites. The built-in radio transmitter also means less stuff to carry, fewer batteries to buy, and fewer systems to troubleshoot. Both units are dead simple to operate and work brilliantly straight out of the box. Along with the built-in radio capabilities, new and improved feature set, and streamlined interface, the Canon 600EX-RT and ST-E3-RT are a really exciting combination and worthy of consideration for those interested in upgrading or entering the world of wireless off-camera flash.

Company: Canon U.S.A., Inc.
Price: 600EX-RT: $629.99; ST-E3-RT: $470
Rating: 600EX-RT: 5; ST-E3-RT: 4
Hot: Built-in wireless radio; increased zoom; improved interface
Not: ST-E3 lacks AF Assist Beam and optical wireless


  • Mario says:

    Since the ST-E3-RT can control the 600EX-RTs in manual mode over radio, I’m seriously contemplating upgrading. I’ve got 3 580EX IIs and the old ST-E2 transmitter. I hated how I couldn’t control my 580ex IIs in manual, but I loved the AF assist beam. So in wedding receptions I usually had the ST-E2 mounted on my 5D mark II, then used a cable and connected a CyberSync transmitter to the ST-E2 to fire off my 580s in manual. Essentially the ST-E2 was a $250 focus beam! But the system worked well in low light, just a lot of moving parts.

    Now I’ve got the 5D mark III (and a mark II still), so these 600s look even more tempting. Radio capacities with and separate transmitters or receivers means much less to worry about. Plus being able to adjust the flashes right from my transmitter is amazing. I tried TTL Pocket Wizards and took them back. I’ve always wanted to be able to control the flashes from the camera to save time. Looks like the 600s might be the best answer.

    But my only concern is low light receptions. There’s no focus beam on the ST-E3. Some are saying just get another 600EX and use it as a master, but does it have all the same control capabilities?

    What do you think?

    • Nick A says:

      Hi Mario,

      Just did my first wedding with a couple of 600rt and the ST-E3 on my 5D mark III. The reception was pretty dark, and was using the 24-105 instead of my 35 1.4. I was afraid I might have trouble focusing, but it worked out pretty good, I missed a few shoots, becuase of focusing.. But nothing critical.