Radio Wireless Communication
Using a speedlite on your camera is convenient especially if you are working alone or you need to be highly mobile and taking photos of a subject that is on the move such as at a wedding or an event. The light from an unmodified speedlite can often be hard and contrasty so not very flattering if it’s being used as the main light. It’s not a bad option if you are just using it as a fill light to fill in or soften hard shadows caused by the sun. However most of the time you’ll want to use the light from a speedlite as your main light source so you’ll want to soften the shadows and change the direction of the light for creative effect. To do this you’ll need to get your speed light off your camera and probably place it in a light modifier such as a soft box to improve the light quality. You can get an assistant to hold the speedlite for you or you can put it on a light stand. Whichever you choose you want the flash to go off when you take the photo. The simplest and most reliable form of triggering your off-camera speedlite is by radio wireless communication or commonly referred to as by radio trigger. For radio wireless communication to work you need something to send the signal from the camera to the speedlite. This is known as a transmitter. This could be a speedlite working in radio master mode or it could be a controller that attaches to the top of the camera. On the receiving end of the signal is a device known as a receiver. This can be built-into a speedlite with the speedlite working in slave mode or it could be a stand-alone receiver attached to the speedlite (by cable or by fitting onto the speedlite’s hotshoe).
Examples of Radio wireless systems:
Canon Radio Systems
The Canon 600EX II-RT has an integrated radio wireless transceiver (transmitter and receiver) and can act as a radio master or a radio slave unit.
The Canon 600EX II-RT can act as a radio master to control the following slave units: Canon 600EX ii-RT, Canon 600EX -RT, Canon 430 iii-RT and various third party speedlites such as the Yongnuo YN600EX-RT II, Yongnuo YN968EX-RT as well as the Yongnuo YNE3-RX receiver which can be attached to E-TTL II compatible speedlites to allow them to act as a radio slave.
Using a Canon 600EX II-RT on a camera’s hotshoe can be a bit bulky, heavy and generally inconvenient as well as being a very expensive transmitter. You could use the lighter and slightly smaller Canon 430EX iii-RT but if you don’t need the on-camera speedlite to fire and you don’t need the auto-focus assist beam then you are best using a dedicated radio transmitter such as the Canon ST-E3-RT. This is half the price of a Canon 600EX II-RT and just a little bit less than a Canon 430EX iii-RT.
Of course there are many other radio wireless communication systems out there.
Yongnuo Radio Systems
Yongnuo have an incredible four radio systems none of which are directly compatible so be sure to check them out carefully before adding them to an existing lighting system.
RT Radio. On their Canon speedlite clones such as the Yongnuo YN600EX-RT II and the YN968EX-RT they use the same Canon RT radio wireless system. They should therefore be fully compatible with the original Canon RT speedlites and ST-E3-RT controller although several people have reported some compatibility issues when using Yongnuo equipment with more recently released Canon cameras. Yongnuo haven’t quite perfected their RT radio system cloning.
YN622 Radio. The Yongnuo YN685 has built in radio receivers that work with the Yongnuo 622 radio system. This system is fully compatible with Canon ETTL-II speedlites. You’ll need a YN622C-TX transmitter and YN622C II receivers can be attached to ETTL-II compatible speedlites including the older Canon 580EX II and the Canon 430EX II.
RF603 Radio. Yongnuo also have a great manual radio transceiver set which works on the RF603 radio system. A pair of transceivers can be used on virtually any camera to fire virtually any speedlite but only a basic “fire” signal can be sent and its not possible to change the speedlite power or use E-TTL II. Excellent for manual flash and even studio lights.
YN560 Radio. Yongnuo also have a YN560 radio system. A YN560-TX transmitter can be used to control their YN560 range of manual speedlites. The transmitter can send information to the slave speedlites to increase or decrease power. The YN560-TX transmitter also sends out an RF603 signal so can fire any light with an RF603 receiver attached (or in-built).
Godox Radio Systems
Godox are altogether much more organised when it comes to their radio communication system. They started off slowly but have now tried to keep all of their speedlites compatible with their Radio X system.