The need to control an off camera flash came about a while back. I purchases an hotshoe extension cable (YONGNUO FC-681) which allowed me to handhold and aim the flash by hand. In itself the cable worked great, however I needed the AF assist feature that the flash provides and aligning the AF assist beam of the flash by hand is next to impossible while looking through the camera’s viewfinder.

So I bought a YONGNUO ST-E2 wireless controller for its AF assist light and in itself works great, but doesn’t control my flash very well in E-TTL mode. Further to that, since the ST-E2 control is done by optical communication, I am afraid that even if a new flash will be able to be controlled by the ST-E2, outside or otherwise dark environments with black walls there may not be much/enough light reflected to be able to trigger and communicate with flashes that are placed behind the camera.

So I decided to combine the E-TTL hotshoe extension cable with the ST-E2 controller. With this setup I get the AF assist beam of the ST-E2 and am able to E-TTL command the flash where ever it may be pointing.

Brief description of the project: I chopped off the hotshoe connector cable at one and, and soldered the wires into the ST-E2 right as they come off the hotshoe.

First chop off the FC-681 extension cable.
Make sure to chop off the end that normally attaches to the camera (not the end that the flash attaches to, although I suppose it doesn’t really matter as both ends have a hotshoe for your flash. Next take apart the ST-E2.

Remove the 4 screws in the battery compartment (in my unit 2 of the screws were behind stickers in the battery compartment) and with a bit of persuasion, the unit should come apart. Remove the circuit board leaving only the hotshoe connections (and the AF assist led connection).

At this point you can have a choice to work in the crammed space of the inside of the unit (by leaving the hotshoe in it’s assembled place) or taking the hotshoe apart to work on the bench with more space. I took the hotshoe apart however putting it back together is a little tricky. The hot shoe is kept in place by 4 long silver screws.

This chart should give you an idea of the wire color in the ST-E2 and which wire they get connected from the FC-681 cable. I would suggest doing a quick check yourself to make sure it all checks out for you.

This is what the connections look like for me. I just spliced into the ST-E2 hotshoe wires, the wires from the FC-681 cable.

And that’s it.

This is what I am left with:

Now I have a Frankenstein hot shoe extension cable which works as expected. The AF assist beam on the ST-E2 unit work as it did pre-hack and the flash also fires properly.