The Canon 7D User Manual (page 119) says for outdoor use, you can be as much as 7 meters (23 feet) away ... so I setup a test as seen below - picture taken with a tripod mounted 50D fired via the wireless remote. It was pitch black outside (best case scenario) and I rotated one 580EX Flash to light up Frankenstein and the other the Headless Horseman. Both had their sensor pointed at the tripod mounted 7D. Manual mode was set to 1/64 (even that was a bit hot at F/5 and ISO1600) and at least three test pictures were taken at each distance. The results were very consistent - both flashes fired every time at 10, 20, and 30 feet. Both failed to fire at 40 feet. So slightly more range than specified, although I'm sure that distance would shrink in daylight. It will be nice when this is all done via RF, since that has potential for much more range and remove line of sight requirements.
One "bug" is that the Canon 7D built-in flash can not use High Speed Sync when acting as a controller. While I would expect no HSS as a "regular" flash (since this eats power), I'm hoping this is an oversight and will be fixed in the next firmware.
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