Why won't my Yongnuo YN468-II fire on a Canon Rebel 2000 (when it works on other cameras)?

Question

So I have a Yongnuo YN468-II that will not fire on a Canon Rebel 2000 (film camera).

What is strange is it will fire on a Canon Rebel T1i, and on a Canon AE-1 (another film camera).

It seems to detect focal length adjustments just fine and when I use an official Canon Speedlight that flash will fire.

I'm pretty sure it isn't a shutter speed issue as I've tried firing at 1/90 and 1/60 and I can put it in manual mode to test; however, even when in manual mode it won't fire.

If there are any ideas or more information that I can provide, please let me know!

Answer 1

My guess is this is a gap in the reverse engineering Yongnuo does for the electronic communication protocol of the Canon hotshoe. The AE-1 is old enough that it's using the film version of TTL/A-TTL, while the Rebel 2000 uses E-TTL, and the T1i uses E-TTL II. Canon flashes can probably detect and switch to the different modes for TTL/A-TTL, E-TTL, and E-TTL II, but maybe the Yongnuo flashes can only recognize the film TTL and eTTL-II signals or were only engineered to handle those two as the most-likely TTL scenarios (or the only ones where YN had gear to test against).

As an example, I have a YN-568EX flash. It works great on my 5DMkII and 50D. However, when I put it on the hotshoe of my Powershot G9, it fails to fire. The G9 is clearly using some variant of the regular EOS hotshoe communication protocol, but it doesn't do E-TTL II. My 580EXII works fine on all three hotshoes, and can even have its manual power level set from the G9. It's clearly been designed to recognize my Powershot variant. The Yongnuo has not.

see also: The EOS Flash Bible's sections on the Canon TTL flavors.