The G12 and any large flash become an ungainly, but sometimes useful, combination. In my introductory remarks about the YN565EX, I noted that it was not purchased for use on the G12 and implied that there were problems. Indeed, the YN565EX should be considered as incompatible with the G12; however, it does work on the G12 in certain modes. Let’s get the bad news out of the way first.
The YN565EX does not work at all – that is, does not even flash – when the G12 is in manual flash mode. This was completely unexpected. I expected some kind of odd ball behavior but it never crossed my mind that the YN565EX would not fire at all when mounted on the G12. Curious, I tried the YN565EX on my G9 only to find the same behavior (after changing batteries in the G9). Next, I tried the YN565EX on the G6 and G3 and discovered that the YN565EX is completely incompatible with those older G series cameras.
On the positive side, the YN565EX does work on the G12 when the G12 is in P, Tv or Av mode. The YN565EX zooms with the G12 zoom and Flash Exposure Compensation can be controlled either by the YN565EX or by the G12. The YN565EX seems to work in either direct or bounce orientation (I say “seems” to work because I did not attempt to check the accuracy of the flash exposure). Again, I’ll comment that the YN565EX is noticeably louder than the 580EX II when flashing. Also, to my eye, the YN565EX produces a more noticeable pre-flash when used on the G12. I would not be confident in using the YN565EX mounted on the G12.
But I didn’t get the YN565EX for direct mounting on the G12; I got it for use in the Canon wireless system. The G12 does not have its own internal wireless controller as does the 7D but the 580EX II can act as the master, or controlling, flash. My first attempts to set the 580EX II as the master flash were unsuccessful and I was beginning to think that the 580EX II was itself incompatible with the G12. Then I discovered that the G12 requires a menu setting to enable the Canon wireless system. As soon as the wireless system was enabled in the G12 menu, the 580EX II immediately became the master flash. Alas, the YN565EX did not respond to the 580EX II as a master when the 580EX II was mounted on the G12.
In my frustration, I got out a Canon 420EX and set it to slave flash mode using the same settings as the YN565EX. Side-by-side with the YN565EX, the 420EX responded to the 580EX II as expected but the YN565EX did not. More frustrated, I removed the 580EX II from the G12 and placed it on the 7D, noting that the settings did not change. When triggered by the 7D, both the YN565EX and the 420EX fired as expected -- end of compatibility tests.
Well, almost the end of compatibility tests. In optical slave flash mode, the YN565EX does respond to the G12 internal flash and also to the 580EX II when mounted on the G12. The YN565EX also responds to the simple Yongnuo RF-602 wireless trigger. These are very useful features.
My conclusion is that although the YN565EX is not totally incompatible with the G12, it is best to declare the YN565EX as being incompatible and therefore avoid the frustration of attempting to remember which settings and modes work and which do not. I won’t be using the YN565EX with my G series cameras except as an optical slave flash or with the RF-602 trigger.
… but I’m still OK with having purchased the YN565EX.