Panasonic has announced a firmware update for the Lumix DMC-GH4, adding tethered shooting and modes to make it easier to take still images from 4K video. The update introduces 4K Photo Mode, which automatically sets shooting parameters optimized for stills and allows 4K capture in a variety of aspect ratios. There is also a Rec Loop mode that constantly shoots and deletes footage from the card - retaining only the last five two-minute clips. The firmwate also brings a 23.98p 4K shooting in MP4/AAC mode.
Other changes include adjustable flash output and greater control over ISO.
The firmware update will be available from Panasonic's support website in October.

Panasonic Announces the Firmware Update Program for LUMIX DMC-GH4 Featuring 4K Photo Mode 

NEWARK, NJ (September 15, 2014) - Panasonic announces the new firmware update program for the LUMIX Digital Single Lens Mirrorless (DSLM) camera DMC-GH4. The firmware will be released to enhance the performance and controllability of the camera, featuring new 4K Photo Mode.
The 4K Photo is a new way of photography that Panasonic is proposing. It encourages users to capture the spur-of-the-moment in high resolution 4K photo by cropping out a designated frame out of the 4K video. With the new firmware, it is easier to get a 4K photo by using the 4K Photo Mode. Once selecting the 4K Photo Mode, recording format / picture quality setting / brightness level are automatically set to the optimum parameters for photo shooting. Users can record high quality video either in 4:3, 3:2 or even 1:1 aspect ratios in addition to 16:9 – all can provide a still image with 8-megapixel equivalent resolution. Each JPEG image cropped out of the video footage complies with EXIF just as a normal still picture. While recording the 4K video in 4K Photo Mode, it is possible to mark the designated portion by just pressing the [Fn1] button. This can reduce postproduction work for searching the spur-of-the-moment worth cropping out. Moreover, 4K video can be recorded continuously with Loop Rec function which keeps saving the 5 newest 2-minute video files. Users can patiently wait for the perfect photo opportunity to come as long as they want keep the camera recording without worrying about the capacity of the SDXC/SDHC Memory Card*1.
There are more functional upgrades such as the addition of 4K video recording in 23.98p (MP4, AAC) and enhancement of controllability over ISO setting or the amount of flash emission. Also, the DMC-GH4 now expands its connectivity with external equipment. For example, the PC software “USB Tether*2” enables remote camera control (shooting, setting or image data transfer) by PC via USB.
The PHOTOfunSTUDIO 9.5PE and Panasonic Image App for iOS/Android will also be updated to support these functional upgrades.   
The new firmware program is scheduled to be released with more information in detail at the Panasonic LUMIX Support Site at http://panasonic.jp/support/global/cs/dsc/ in the beginning of October, 2014.
*1 Use SDXC/SDHC Memory Card compatible with UHS Speed Class 3 (U3)
*2 *For more information on PC software “USB Tether”, please visit the website of Promote Systems. http://www.promotesystems.com