Here is the lens mounted to the Lumix GH4:
So what exactly does this firmware update do? If you follow online forums, you will see some few, but quite vocal, people complain about "micro jitters" when recording video using this lens. Based on the press release explanation from Panasonic, it might appear that the firmware addresses this issue:
"Improved the stability of O.I.S.[Optical Image Stabilizer] in Motion Picture recording (When using DMC-GH3/GH4)".
To test the effect of the firmware upgrade, I recorded movies both before and after the upgrade, to be able to directly compare the results. The videos were recorded in 1080p mode, at 60FPS. T be able to see any "micro jitters", should they appear, I used the largest aperture, f/2.8, for the fastest shutter speed. That should allow you to see any instability, rather than burying it in motion blur.
Here are the comparison videos, with firmware 1.1 to the left, and firmware 1.2 to the right:
When recording, I held the camera at waist level, looking down into the viewfinder:
It does look like the video stream made after the firmware upgrade is more stable. It seems more calm.
Some have complained that the same problem can be found also with the newer Lumix G HD 14-140mm f/3.5-5.6 super zoom lens, that it too suffers from a vibration when recording videos. Perhaps Panasonic will address this alleged issue with a firmware upgrade later?