Aokatec wireless flash triggers with Olympus

[Long ago I wrote something on a Flickr discussion group about using Aokatec TTL radio triggers with Olympus cameras, and I later had to delete the photos that went with it because my Flickr account was getting full. People still occasionally ask me questions about the info, though, so I’m summarizing it here.]

A while back I bought a set of Aokatec AK-TTL radio triggers, hoping that I could use them with the wireless TTL system of my Olympus E-M 5.

Guess what: it works!
This is kind of a big deal because until now, there has been NO way to use Olympus’ excellent wireless TTL setup with a radio system. You’ve been limited to the optical triggering built into Olympus camera bodies and flash units. Like other manufacturers’ optical wireless systems, this works great at short distances and under subdued light – but gets janky at longer ranges, in bright sunlight, or if there isn’t a clear line of sight between the control flash and the receiver flash.

Aokatec gets around these limitations by using a radio-frequency “repeater” system. The transmitter reads the master flash unit’s opticalcontrol pulses (by sensing the electromagnetic burst from the flashtube) and translates them into equivalent radio pulses. The receiver captures the radio pulses and translates them back into optical pulses via a little plug-in infrared emitter, which you strap onto your receiver flash so it sits over the flash’s optical signal sensor. This repeater concept was pioneered by RadioPopper and is well proved by now.

Mounting the emitter

The trickiest thing about getting the Aokatec units to work with my Olympus gear was finding out exactly where to put that little IR emitter. The receptor on the front of my Olympus FL-36R flash unit is covered by a large piece of dark red plastic that also houses the AF light and the autoflash/slave eye; I couldn’t see through it well enough to spot the control sensor. So I carefully pried off the red plastic piece:

There it was, down low on the left-hand side. With the plastic cover back on, I was able to line up the Aokatec emitter correctly by aligning it with the top and left edges of the word OLYMPUS printed on the cover, and secured it in place with one of the supplied elastic bands:

Update: I’ve since found that the Aokatec receiver also works fine with the Micro Four Thirds version of the inexplicably popular* Nissin i40 flash. This flash works as a remote unit with the Olympus RC system, just like the FL36R. For the Nissin flash, the magic spot to position the Aokatec emitter is centered over the Nissin nameplate on the front, with the top edge of the emitter lined up with the bottom edge of the white LED panel above the nameplate.

Mounting the transmitter

The Aokatec transmitter comes with a clever little bracket for use with pop-up flashes, and a standard foot for shoe mounting. But I couldn’t use either of those: the little folding flash unit that came with my Olympus E-M 5 occupies the camera’s flash shoe. (Incidentally, although this flash is tiny, it works as a full-fledged wireless TTL controller via the E-M 5’s flash control menu.)

The best I could do was attach the transmitter to the top of the flash with another elastic band. Fortunately, placement of the transmitter turned out not to be critical: it can sense the flash firing pretty much no matter how it’s mounted.

(A slight problem: Pushing down the flash head shuts it off, and the extra weight of the Aokatec transmitter made it a bit prone to push down accidentally. I slid the elastic band all the way back to the hinge to make it a bit less likely to close on its own.)

Later, I discovered another solution that’s not quite as fiddly. As noted above, the Aokatec kit includes a mounting bracket for positioning the transmitter over a pop-up flash. It turns out that this bracket comes apart, and I discovered I could attach the shoe portion directly to the back of my little Olympus flash using cyanoacrylate (“crazy”) glue:

This modification looks a bit ugly (mostly because I didn’t do a very neat job of gluing it) but it does hold, and it doesn’t interfere with normal use of the flash (although it makes it a bit bulkier to store.) With the shoe in place, you can attach the Aokatec transmitter so it sits neatly above the flash head. There’s enough free space to turn off the flash by pushing it down (as shown in the photo) or turn it on by pulling it up.

I’ve long since lost the test shots I made for the original posting, but rest assured that the Aokatecs work with all the options of Olympus’ RC remote flash system, including high-speed sync. Range depends on conditions, of course, but outdoors at night I was reliably triggering flashes from as far away as 200 feet (it might even be longer, but this was as far away as I could get without startling the neighbors.)

So aside from the fiddly transmitter and receiver mounting, the Aokatec system seems like a win: no-sweat, no-bother radio TTL for Olympus! I’m stoked…