GH4 need a fast lens

[Lindquist]

http://www.adorama.com/ipc4217.html

thinking about getting this lens since it has OIS and Auto Focus for my 4k video for good low light performance.
anyone else anything besides this thats under $500?

 

[DeeZiD]

Great lens. Used it for many projects since I've bought it last month
But autofocus in video (especially 4k video) is really no option, jumping every time...