YN 560 TX with Sony A7
There are a lot of solutions for wireless flash triggering out there, some for many years already. Big names are in the game like pocketwizard. You can find triggers just with a contact and some with TTL. TTL solutions are mainly for the two big ones, Canon and Nikon, from third party supplier or from Canon and Nikon themself. I have used years ago the pocketwizard TTL trigger with the Canon 5D, it was working nice a reliable, but was not cheap cause you need flashes that can understand the internal TTL comunication. Thoses flashes cost a few hunder bucks and if you need more than one, you realy have to think about the investment if you don't use those triggers and flashes on regular bases.
But Canon times are over, and I'm not the big flash user, I haven't uses flashes for years, so that I'm thinking about a cheap but realiable solution for my Sony A7. I have tested China trigger in the past already, but years ago they were just crap. Not reliable at all. But times are changing and so the production quality. These days everybody who heard the word "strobist" have heard the mame Yongnuo, a chinese flash company. I have used the 603 II triggers already once and they were fine. Important thing for Sony users, you don't have to modify them anymore.
Now I had to buy some flashes for a project and came back to that company. I went to amazon and found the YN 560 III, great solution, a easy to use wireless flash with build in receiver, so no extra receiver needed. Great. Then I found the YN 560 TX, a wireless flash trigger with remote control for the YN 560 III flashes. And it was cheap. Ony day later I had a few flashes and the YN 560 TX on my table. Flashes and the transmitter were build in a nice quality, no complains, one flash was not working, so I had to send it back. Easy these days with amazon. Now I have all flashes working. I have the Nikon version for the flashes and the transmitters but it will not make difference if you would use the Canon ones for Sony. It will just use the contact closure for triggering the flash.
The only thing you have to do is to make a contection between the 560 TX and the flashes, define the groups, all pretty easy. There are thousands of youtubes videos about that.
It is working quite nice with the A7, triggering reliable up to 1/200 of a second. The control of the flashes via the buttons on the TX is very easy, and that is important if you don't use the setup on regular base. You don't have to read a manual every time you use them.
As a conclusion I can say that the combination YN 560, YN 560 TX and the Sony A7 is working nice, without any complains. The control is easy going and the results are good, the flashes have a lot of power. The whole setup is pretty cheap you get a set with two flashes and one TX trigger below 180 $. That is less than one single Nikon flash. OK, there is no TTL, but you can use flashes in manual mode without problems. Overall, I can recomment this combination!