I am a big fan of Canon's transition from infrared remote flash to using radio. The 600 EX RT is a very powerful unit and by adding Canon's effective but pricey ST-E3-RT, you could control a bunch of 600s from the camera without using up a flash head on camera. It works, but what if there were a more cost effective alternative?There is. It is from Yong Nuo. This company is a known quantity amongst hot shoe flash people. Training master #Scott Kelby has advocated use of Yong Nuo flashes for some time. I have clients who live by the Yong Nuo radio triggers because they deliver radio based TTL flash control without inducing a month of Kraft Dinner for meals. They just work. Yong Nuo even announced their clone of the 600 EX RT although that remains scarcer than hen's teeth for the moment. At the same time, they announced the YN-E3-RT. It's their version of the ST-E3-RT and the big difference is investment. The Canon offering is great, but pretty expensive. The Yong Nuo does what the Canon does and is less than half the price. Yes you will be likely ordering it from China. Mine took about 10 days to arrive.
There are some pretty cool benefits to the YN-E3-RT over the Canon unit. Most importantly for me, is that it adds infrared focus assist. Canon had this in the ST-E2 unit that worked with the 580 EX series. It was not a well loved offering but it did have IR focus assist. When the E3 from Canon came out, serious flashers asked WTF? We're often shooting in conditions where the lighting that brings on the need for flash also doesn't provide enough light for regular Autofocus. By including focus assist in the YN-E3-RT, Yong Nuo demonstrates that they listen to buyers, something Canon frequently has a problem with.
If you use the Canon unit on cameras older than 2012, max flash sync speed is 1/125. Not awful but not what the camera may be capable of. The Yong Nuo eliminates that barrier. It also means that if you have an older camera, you can get group support in the flash system a missing unless you have a newer product with Canon's offering.
The Yong Nuo also arrived with a bunch of sync cables, that I don't recall getting with my Canon unit, although I may have misplaced them.
From a construction perspective, the units look identical. Canon allows for either green or orange display, the YN does green. No biggie. I found the buttons on the Canon more precise and with a nominally better fit but if I did not have the side by side comparative capability, I probably would not know. The Yong Nuo unit has a USB port so you can update the firmware on it. The port is in the same place as the sync cable port on the Canon. The YN-E3-RT comes in a padded nylon case that is virtually indistinguishable from the Canon model.
Canon's unit sells for about $385 where I live. The Yong Nuo cost me $140 through Amazon Canada. Some have complained that the IR AF assist in the YN doesn't cover all the focus points. True, but the Canon unit doesn't cover any since it has NO autofocus assist.
Judge for yourself. The Yong Nuo solves a couple of legitimate issues for me with IR focus assist and no throttling of flash function on my older 1D Mk IV. I'm pleased so far.