Get Olympus SHG at B&H Photo.
Video shooters generally have a bulky 'rig' wrapped around a relatively tiny camera. And so while lens size and weight might be problematic for still shooters, I’d urge video shooters to take a good look at the Olympus Super High Grade (Olympus SHG) lenses for shooting video (see various reviews in Guide to Mirrorless, look also for “SHG” on the table of contents). Being Four Thirds mount, the Olympus MMF-3 Four Thirds to Micro Four Thirds lens mount adapter is needed to mount on a Micro Four Thirds camera like the Panasonic GH4.
The Olympus SHG lenses are exceptionally well corrected for color and aberrations and offer an exceptional build quality. Reference lenses. They are as large and heavy as DSLR equivalents, yet they the cover only a Micro Four Thirds sensor—getting high performance generally demands larger lenses (without excessive cost), and the size of the Olympus SHG lenses is in good measure a direct consequence of the high optical goals.
Every video shooter’s bag should also have the Panasonic Leica 42.5mm f/1.2 Nocticron, which might well be the best Micro Four Thirds native mount lens available today.
Size and weight are daunting for still shooters, but in a video rig setup, the ergonomics are far better than nearly all native Micro Four Thirds lenses for pulling focus and zooming.