Sony has announced the new firmware v1.1 to fix the inability of the camera to record 4K internally at the same time as outputting an image to externally via the HDMI port.
Got to put my hand up and say I have never tested this out on my FS5 but for those using 4K 25p 8bit I suspect its been a frustrating time.
Sonys download site tells us the following…
1.) External output and face detection support when recording in XAVC QFHD (4K mode)
You can get the download here : http://www.sony.co.uk/pro/support/software/SW_122115_PSG/1
After installing new firmware V1.1 my experience was that the FS5 had returned to default settings! Apparently other operators have experienced this and other problems
Sony have released the version 1.1 firmware update for the PXW-FS5 which allows you to output 4K over the HDMI while recording 4K on the SD cards. However it does appear that at the moment at least it is impossible to output 4K, Record internal 4K AND have a picture on the LCD or EVF. Lets hope this gets resolved later in time. It also adds auto focus face detection in 4K.