Why does the ST-E3-RT limit shutter speed on a Canon 5D Mark II with a 600EX-RT?
Asked 12/25/2012
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I'm using a Canon 5D Mark II with an ST-E3-RT transmitter and a 600EX-RT off-camera in E-TTL. Both the transmitter and flash are set to HSS, but when I set the shutter faster than about 1/100–1/200 sec, the transmitter shows a Tv warning/exclamation mark. If I mount the flash directly on the camera, high shutter speeds work normally. Why does this happen with the radio transmitter, and is there any way around it?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
10
Refer to page 19 of your ST-E3-RT manual. It specifies that when used with camera models released prior to 2012 (so, anything but the 1DX and 5D mark III at the time of this post) you lose high speed sync and your max sync speed is "one increment slower" than whatever it would normally be.
The flash sync speed is 1 increment slower
Check the flash sync speed (X = 1/*** sec.) of your camera, and shoot with a shutter speed up to a maximum of 1 stop slower than the flash sync speed (Example: When X = 1/250 sec. to 30 sec.). Also, high-speed sync shooting is not possible. When you set the shutter speed 1 increment slower than the flash sync speed, the warning icon will disappear.
Sucks that you gave Canon a bunch of your money for this feature and this is how they treat you. Could have purchased another flash or a PocketWizard and have been better off.
Edit: Right now the difference in price between the 600-RT and the ST-E3-RT is about $200 for which, if you (or anyone else reading this) bought the flash over the trigger, would gain the benefit of the full sync speed and high speed sync over IR and the benefit of a second flash. Also, a cheap $20 radio trigger would allow for the full sync speed, but at the expense of high speed sync and ETTL.
Originally by user9510. Source · Licensed CC BY-SA 4.0
user9510
13y ago
0
Generated from our catalog & community — verify before relying on it.
This is expected behavior with the 5D Mark II and the ST-E3-RT in radio mode. Canon states that on older camera bodies released before 2012, the ST-E3-RT reduces usable flash sync speed to one step slower than the camera’s normal X-sync, and high-speed sync is not available in radio mode.
Why: the radio system adds timing/communication overhead, and older bodies were not designed to coordinate that two-way radio communication at full sync speed. A flash mounted directly on the hot shoe, or controlled optically, does not have the same limitation.
So with a 5D Mark II, the warning appears because you’re setting a shutter speed faster than the reduced sync limit for radio triggering. The fix is simply to stay at or below the allowed sync speed for that setup. If you need faster shutter speeds or HSS, mount the flash directly on-camera, use an E-TTL cord, or use an optical control method instead of RT radio triggering.
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