Sorry if the following issue has been covered.
Background: In June 2017 I got my first M43 Camera – the Olympus E-M1mkII. It's been a pleasant experience overall but the automatic focus bracketing in particular has impressed me.
During the off season here in Sweden I've been hooking my E-M1mkII to my studio setup – Cognisys Stackshot-based. And I've run into an unexpected issue: The EM-1mkII freezes directly after exposure, when set to shoot in high resolution mode and triggered by the Stackshot. Normally, exposure in HR-mode is followed by a processing bar where the Camera supposedly does some advanced calculations during a few seconds before the image is written to the card. But when triggered by the Stackshot unit, the camera seems to shoot the series of sensor-shifted images, and then freeze indefinitely with a black screen and only the HR-icon showing in the upper right of the screen.
There are only three ways of forcing the camera out of this state:
1) Half-pressing the shutter button
2) Disconnecting the remote release cable
3) Removing the camera battery
The first two will result in an image being written to the memory card as if nothing weird had happened.
Everything seemed to work well with a regular cable release, so at first I thought it was some issue with the signal coming from the Stackshot and I did a lot of experimentation with different TPulse-settings (to no avail). I contacted both Olympus and Cognisys but neither one had heard of this issue before. Cognisys was quite helpful and provided me with a lot of info to go forward with my troubleshooting while Olympus just seemed convinced that this wasn't their problem.
Nevertheless, I soon realized that the problem was indeed Olympus "fault". As far as I can tell, they must have done something weird with their HR-mode implementation and how it responds to remote triggering. Everything works fine as long as the high resolution mode (achieved through sensor shifting) is NOT used.
The cable release uses a 2.5 mm jack connector. Closing the tip and the base circuit results in a full press and connecting the ring and the base equals half press. At least that's how it seems to work according to the standard – my Canon 760D responds like this and the Olympus EM-1mkII does as well – that is, as long as the Olympus is NOT set to HR-mode.
But for some reason, in HR-mode (and ONLY in HR-mode) – the EM-1mkII requires a full-press AND a half-press in order to finalize an exposure. A simple full-press signal will cause the camera to stall until the battery runs out, unless you do one of the three things mentioned above.
Fortunately the solution to this problem is as crude as it is simple: just short out the tip and the ring of the 2.5-connector and everything works fine!
The second image shows my solution: connecting the tip and the ring will force a half-press + full-press signal. This will cause the EM-1mkII to work as expected in HR-mode (as well as in all other modes!).