The Canon 150-600 L and the GH4 meet for the first time :

11101 & GH4 first date. - YouTube

Testing the GH4 Digital Zoom and Ex. Tele Conv :

GH4 Digital Zoom vs Ex. Tele Conv Test - YouTube
This test was shot with a CZ 35-135 T*
YT compression makes the mov v.s. avchd comparison rather useless and I'm not even sure that I used the same shutter speed .. so