Low light performance is just happens to be the most important video feature, it is the one feature that can get you the shot or miss it. The GH4 is basically useless for video past ISO 1600, and not that great at 1600 either. The 5D3 gives great results up to about ISO 10,000 and with Magic Lantern you get zebras, peaking, magic zoom, and a ton of other goodies, so the GH4 doesn't cut it for me. The Sony A7s will be a great option when they get a good selection of native FF lenses, but Canon will probably have an offering before Sony gets the lenses made.
Also, is there DOF on the Gh4 without the speedbooster? Just curious.
Aaaaand that's why I wait for the Sony a7sII ... likely adding the 3-5 axis sensor stabilization and maybe fix that rolling shutter issue. I could care less what glass Sony makes for it. Hello metabones and Canon EF glass.
I wasn't too keen with mark 1, but that 5-axis man...
In fact, add 1080/120 and you have gold... pure gold
I use to think high ISO was super important, but then I learned how to light things. Now I think anything clean over 3,200 is nice, but not necessary. Maybe if all one has is a kit lens at f/5.6 I can see the importance.
Also, don't forget that a Speedbooster on the GH4 gives you both a Super35 (~APS-C) FOV AND an extra stop of light. When other cameras need ISO 3,200 for a given scene, the GH4 with Speedbooster will give you the same exposure at ISO 1,600. And that combo is still $400 cheaper than the A7s and $1000 cheaper than the Mark III.
And the A7s can mount any type of glass in the world. Not sure why you'd hold out for native Sony glass....
Yeah, but just to add... with regards to lighting... its a drag to lug around a generator all the time (if you are outside). And, if you're talking about battery LEDs... those sony batteries are expensive!
I'm hearing a lot good things about that speedbooster, never thought it can do super 35 FOV...
I have a friend who got the speedbooster with the Sigma 18-35 1.8 (turned it into 1.2 - Have you ever heard a zoom with 1.2???)
All of those things are coming sooner than later.
If I was starting from scratch I might not go with Canon right now, but I don't see anything tempting enough to make me risk selling my and replacing it with another brand, especially since this is all a game of leapfrog and Canon is not sleeping.
The 5D3 is still the best all around combo video/photo option I think: it does great low light for both video and photo, it has good AF for photos, lots of lenses, built like a tank, great ergonomics, has magic lantern. I am tempted a bit by the Sony A7s (although some say it's a bit fiddly), but I'll wait and see what they do with the mark II. In the meantime Canon may leap ahead. I am actually considering the C100 markII ... the new viewfinder and LCD look great, and that is a really useable camera.
Some people love the GH4, but working alone in a variety of poorly lit environments where I can't control the lighting, it's just not going to do the job. The 5D3 can deliver great video without intruding on anyone or announcing itself with lights, the C100 even more so, and that's really important for documentary and ENG.
I hope Sony updates the A7s with IS and beefier grip like the A7II ... that might be interesting!