Speedlite 600EX-RT & Speedlite Transmitter ST-E3-RT
Let’s be clear: The Speedlite 600EX-RT radio wireless operation is compatible with nearly any EOS digital SLR for use of wireless flash operation off-camera.*
  • Whether firing a single Speedlite 600EX-RT off-camera, up to 15 Speedlites evenly, or in multiple A:B or A:B C groups, any EOS digital SLR can be used.
    • Users do not need to upgrade to an EOS-1D X or EOS 5D Mark III
  • Original EOS-1D and EOS 1-Ds cameras, and all 35mm film-type EOS SLR cameras, cannot perform E-TTL auto flash with radio-based wireless control. All “Mark…” series versions of the EOS-1D and EOS-1Ds cameras are E-TTL compatible.
However, There are a Few Limitations to be Aware of:
  • With EOS models other than the EOS-1D X and EOS 5D Mark III, if radio-based wireless flash is used, maximum sync shutter speed is one stop slower than normal X-sync (or flash synchronization setting) would be.
    • Example: With the EOS 7D, normal maximum shutter speed with flash is 1/250. When using radio-based wireless flash with the Speedlite 600EX-RT, the fastest guaranteed speed becomes 1/125th second.
    • Additionally, this must be set (or accounted for) by the photographer; the camera will not automatically adjust itself.
  • Shutter sync timing with flash was changed in the new EOS-1D X and EOS 5D Mark III cameras to accommodate the new radio-based wireless flash system.
    • Accordingly, these cameras offer full range of sync shutter speeds, up to the normal top X-sync speed (1/250 on the 1D X, and 1/200th on 5D Mark III).
  • High-speed sync during radio-based Wireless flash shooting is only possible with EOS 5D Mark III and EOS-1D X cameras (as of March, 2012).
    • As with the optical-based wireless flash system, second-curtain flash sync is not possible, and cannot be set.
    • Note: When using second-curtain flash fire the flash toward the end of a long exposure as opposed to in the beginning.
  • Regardless of camera used, the radio-based system is limited to working with a maximum of fifteen EOS Speedlites 600EX-RT flashes used off-camera.
    • Unlike the previous optical-based wireless system, which theoretically had no limit to the number of flashes that could be used, the radio system is indeed limited to fifteen units in total — regardless of the number of flash groups or the flash mode used.
  • As noted before, the new Group firing mode (up to five separate groups) is only possible with EOS-1D X, EOS 5D Mark III, and subsequent models.
  • The original EOS-1D and EOS-1Ds cameras are not able to perform Linked Shooting with the new Speedlite nor the Transmitter unit. (All “Mark…” models are OK for Linked Shooting.)
  • When using Speedlite Transmitter ST-E3-RT, automatic E-TTL wireless flash is not possible with certain cameras such as:
    • All 35mm film-based EOS SLRs, including EOS-3 and EOS-1v, as well as with original EOS-1D and EOS-1Ds models.

What's in Canon Speedlites Click here to see more information about Canon basic features, functions, shooting modes and accessories.

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