Inconsistent TTL results when flash used off-camera (YN565 EX II)

Question

I've got a Yongnuo 565 EX II that meters flawlessly when attached to the hotshoe of my 60D, but is very inconsistent when used off camera and slaved to the built in flash unit.

It frequently doesn't fire at all (either during an exposure or when toggling AEL), and when it does fire the exposure will vary between underexposures and nuclear overexposures, with very rare pops providing the correct exposure.

This doesn't appear to be a range or line of sight issue, as I've tested many different flash-camera positionings, and I suspect it is probably one of the pitfalls of using third party hardware, but like I say the TTL metering does work excellently on camera.

So my question is twofold. First, Is it usual to experience this sort of difference between on- and off-camera TTL flash when using Canon-branded speedlites? Second, can anyone with experience of Yongnuo units say whether essentially useless off-camera TTL performance is to be expected rather than just erratic but still decent behaviour?

Answer 1

I just took a few test shots with YN-622C triggers and my YN-568EX (I usually use them in M, so hadn't thought to test eTTL function), and with the single speedlight, if I had wireless and groups on, I was getting consistent underexposure. If I turned wireless off, eTTL exposure was spot-on. I did NOT get inconsistent exposure or missed fires. I also tested with my 580EXII as master unit (I have a 50D, so my pop-up can't act as master), and that worked ok, too. My YN-568EX is really no worse-behaving than my Canon 580EX or 580EXII in this regard. eTTL, as with any metering-based autoexposure system, can have variance, may not be spot-on, and can be annoying, but it should usually get in you in the ballpark. And wireless (in the proprietary optical system) or on-camera should not make much difference.

Just to cover all the bases, for the misfires, make sure that you're waiting until the flash recycles before pressing the shutter button. Use the recycle beep to notify you if you're not sure. Weak batteries might also cause an issue here, if it's taking more than 3s to recycle between bursts. This could also account for fluctuating power levels if the flash hasn't fully finished recycling before you fire it off again. Check how your FEC is set, as well, and make sure that your settings are kind to your flash. The YN-565EX is only slightly more powerful than a 430EXII--if you're trying to shoot in the dark at f/16 and iso 100, you're probably popping off at full power and you may still be underexposing. Speedlights are the low-end of the power range, flash-wise. Recommend iso 400 and f/4 as starting points.

It is not my experience that Yongnuo gear in wireless eTTL is a total shambles. However, I've read enough and researched enough about Yongnuo gear to know that early adopters of new models immediately after they've been released may end up being inadvertent beta testers. The 565EXII was only released earlier this month (June 2014), so that may be a contributing factor. There have also been reports than the YN-568EXII has issues with eTTL (it supposed works better in Average than Evaluative), and the 565EXII may have inherited that, if they're sharing components/design.

You might want to consider returning it. Yongnuos are cheap for a reason. There are reasons to pay more for OEM gear. IMHO, Yongnuos make great 2nd, 3rd, and 4th flashes (especially if you're going for the simplest manual-only flashes--less engineering to go wrong), but for a first/only flash, it may be worthwhile to save up a bit more and get an OEM unit.

Answer 2

I have seen a similar problem. I have a 565EXII and Canon 70D. On-camera, exposures are correct. Off-camera, with Sc (Canon Slave) mode, the usual result is gross overexposure. (> 3 stops). I haven't used another flash in optical EXIF slave mode to know whether the problem is with the flash or the camera. I have done a lot of tests, and observed the following:

1. Exposure is more likely to be correct using 18-55mm kit lens than 50 mm f1.8.
2. Exposure is more likely to be correct using ratio flash than external only.
3. Large underexposure sometimes occurs even though flash appeared to fire.

My testing was all indoors in a relativly dark situation. I tested in Program and Aperture modes. I am aware of the low battery issue, and tested with freshly charged NiMH batteries. I am expecting off-camera EXIF to work with this flash. Is that unreasonable? In any case, the problem is nothing if not inconsistent. I also don't think FEL is working right, but I don't have experience with that. I assume the external flash should always fire when FEL is pressed, but it doesn't always. I bought my 565EX II December 1, 2014 from Amazon.

Anyway, if you just want it to work, your best chance is to use ratio flash -- that made a big difference for me.