Being able to use your Speedlite (Canon term) or Speedlight (Nikon term) or Camera Flash (Sony term) OFF your camera via a wireless built-in 2.4 GHz radio trigger system, has been a godsend that most of us take for granted.
The traditional way of triggering speedlites pre-2012 was by using 'wireless optical remote' and was always a bit hit-and-miss. As it would rely on one speedlites strobe light to trigger the other nearby speedlites, it wouldn't reliably work through objects and walls, nor if there was bright ambient light from the sun or floodlights. And the trigger range was usually limited to under a 4-8 meter radius.
So when Canon released the original ST-E3-RT Speedlite Transmitter back in March 2012, it unlocked the ability to set up multiple lights very easily, at greater range and response, and at a reasonable price.
You could match the transmitter with the 600EX RT Speedlite, and either hand-hold the flash with a small light modifier attachment to create three quarter or Rembrandt lighting. Or you could even place them on light stands. It was the perfect, entry level way to set up three point lighting if you were on a budget, or needed to travel light.
But since then, with the release of the Canon EL-1 Speedlite (release Feb 2021), the original transmitter was unable to match the incredibly low output of 1/8192 of the total maximum output (i.e. 1/1). To put this into context, that is 6 stops lower than the usual 1/128 minimum output of the Canon 600EXII RT.
This led to the ST-E3-RT (Ver.2) being released back in Feb 2021 to address this issue.
Just recently, Canon has unceremoniously released the ST-E3-RT (Ver.3). There seems to be no official press announcement, but they have quietly added it to their website and it is now available for pre-order on retail websites.
And it does seem fairly understandable why they didn't do an official release as there doesn't seem to be a consequential upgrade from the Ver.2. Upon looking at the official Canon specifications of the Ver.3 vs Ver.2 sheet, apart from being 4g lighter, there is nothing that stands out as a meaningful upgrade.
On the Canon website it states: Speedlite Transmitter ST-E3-RT (Ver.3) supports wireless second curtain sync for the EL-1 when fired remotely, plus 1/8192 nuance lighting and flash exposure (FE) memory.
So there you have it. I wouldn't feel the need to rush out to buy one – if you have the Ver.2, but if you don't have one already, a speedlite transmitter is an important tool in your kit – especially if you are an event or portrait photographer.
You can read more about the transmitter on the Canon AU website.
P.S. For those uninitiated with WHY you want to have an incredibly low output of 1/8192, this enables you to use flash when for example, you are shooting a low light event at 32,000 ISO at f/1.2. To use a flash at the normal minimum of 1/128 of maximum power would blow-out the image by 6 or more stops – depending on how close you were to the subject.
