It may be the grudge match no one is asking for, but I own both these cameras and use them almost daily for paying shoots. So if you're in the market for a new or used camera and your budget is between $1000 and $4500, read on.
The GH4 will always be the cheaper of the two options. As of this writing, the GH4 is $1300 at B&H or $1700 with the YAGH unit which adds XLR inputs, 3G-SDI, HD-SDI, and a full sized HDMI output. WARNING: If you buy the YAGH version your camera will not fit into a cage and you will need an external power supply to the YAGH as it does not work off the GH4 battery.
$1300 for a mirrorless, 4K camera is pretty great, but if you're like me and you have a whole bunch of EF lenses, you'll need an adapter like a Metabones Speedbooster to use them. That can add to the cost of this camera significantly, but will also help to achieve a more shallow depth of field which this camera struggled with out of the box due to it's smaller sensor.
The C100 Mark II is now priced at $4500, a move Canon made on the 1st of this year to compete with Sony's FS5. The C100 is a cinema camera and unlike the GH4 needs nothing additional to get clean audio and beautiful visuals. The sticking point for many may be that the C100 is an HD camera, and does not support any resolutions higher than 1920x1080. The Mark II has a Super35mm CMOS sensor and the images that come off that sensor are beautiful when put into the right hands.
WINNER: As far as price is concerned, the GH4 has the advantage, even for those who will need to purchase an adapter to use EF, E, or Nikon glass. The YAGH interface will add XLR inputs but at a cost of needing external power. If you just want to go out and make nice visuals, the GH4 will get you there at a cheaper pricer point, but to make it as full featured as the Mark II you'll need to rig it. The YAGH unit and the need for external power turns the GH4 from a compact handheld camera to something that needs to be on a shoulder rig or sticks, instead of simply sitting in your hand.
Both of these cameras write to SDXC cards which are cheaper than ever. They each give you the option of recording externally to any one of the growing number of offerings from Atomos, BlackMagic, Convergent Design, etc. Both will give you a clean 4:2:2 signal to an external recorder, but the GH4 will give you a true 10-bit out while the Mark II will not because it's maximum output is 8-bit.
On the flip side, the C100 Mark II has two SD slots which enable continuos recording (if you fill one card while rolling it simply continues writing to the second card slot) or you can write to both cards simultaneously if you're super anal and always worry about losing footage.
WINNER: To close to call so this one is a DRAW.
The GH4 now has V-log, an addition which is did not have for the first year it was out. So is V-log any good? Well it adds about a stop of dynamic range to your image but it makes it much harder to expose without using the histogram. Your lowest ISO for shooting V-Log is now IS0400 and let me tell you what happens to this camera at ISO400 - NOISE. The GH4 does have some nice profiles like Cine-D and Cine-V and you can go into each profile and tweak to your hearts content but it sure does take some time and patience to find a good setting. That doesn't mean that your new custom profile will work with each situation.
On the other hand, the Mark II has C-Log and I love it (it also has Wide DR for those who don't want to do a lot of post grading). As I learn more about color and grading in post I've been able to create images with the C100 Mark II that look awesome.
WINNER: C100 MARK II all the way.
I'm going to make this very easy for you to understand - The GH4 is not a low light camera. The base ISO is ISO200 and you will start getting noise in shadows at IS0400. ISO800 looks like crap and I wouldn't even consider using ISO1600 or ISO3200.
The C100 has a native ISO of ISO850 and its range is ISO320 to ISO102,400. I don't see noise in the blacks until ISO6400. It may not be the low light king, but it's certainly up there.
WINNER: C100 Mark II - If you shoot docs or events the C100 is the camera to pick up.
EVF AND OLED
I really like the touch screen OLED on the GH4 but the OLED on the C100 Mark II is quite nice as well. Both cameras allow you to rotate the screen into different positions (note that depending on what cage you buy for the GH4 that movement may be restricted)
You have the option on the Mark II to view your image with a LUT applied, especially useful when shooting C-Log. I'm not a pixel peeper but both EVF's are also good. I like the ability to turn off the EVF on the C100 when it's not in use and save battery power.
WINNER: In my opinion it's a DRAW.
This one is pretty clear cut - the Mark II has a top handle which adds two XLR inputs and also has a mic built into the body to capture a scratch track if necessary.
Without the YAGH interface unit, the GH4 has a basic mic for scratch and an input so you can use a Rode VideoMic or rig this unit for audio with something like a Juicedlink or Tascam.
WINNER - having to rig for audio sucks. C100 Mark II is clear cut winner here.
This is an interesting category. Neither of these cameras are exactly slow motion beasts. If you're looking for slow motion the FS5 may be a better choice for you with 240fps at 1080.
The GH4 can do 96fps which it conforms in camera for you but it also introduces noise in the image.
For me, shooting 60fps on the Mark II is all I really need. Your needs may be different but for me the winner is...
WINNER - I guess it's a DRAW
The C100 Mark II has a built in ND behind your glass up to 6 stops. The GH4 has no ND. You'll need some ND in front of your lens. Now who wants that. Not this guy.
WINNER - Obviously, the C100 Mark II
You can fly either of these cameras on a gimbal, depending on what gimbal you own. I have the DJI Ronin and am able to balance either of these cameras within minutes. I do remove the hand grip and top handle on the Mark II when using it on the Ronin. The EVF of the Mark II does prevent you from getting a full tilt as the EVF hits the back bar. This may not be the case on gimbals made by other manufacturers.
The GH4 sits very compactly on the Ronin and both are well suited to this type of use since they are both very light cameras.
WINNER - really depends on what and where you are shooting. I prefer to fly the Mark II but the GH4 is also solid. DRAW
Both of these cameras have wifi. The C100 outputs a nice signal to a phone or tablet and can be controlled. It's a nice feature if you need to mount your camera to somewhere hard to reach or on a gimbal.
The GH4 does have a nice 4K Photo Mode which allows you to shoot video at 29.97 and grab 4K frames from it. This makes it easy for a photographer who needs to get an action shot to roll video and grab a still at higher and lower shutter speeds.
The ergonomics of the C100 Mark II are great. Loads of customizable buttons, a removable hand grip with a menu button and programmable button, and start/stop plus a removable top handle.
WINNER: C100 Mark II just has more extra features that compliment it.
To be consistent with what I always say, cameras are just a tool. I know what I typically shoot and what works for me. That may not be the same for you. There are definitely some things I like about the GH4 (4K, touch screen OLED) that I wish the Mark II had, and the GH4 is no slouch, but overall, the C100 Mark II is a real cinema camera which makes sweet-ass images and is sought after by clients. FYI - No client has ever asked me to film on a GH4.
If you have the money and want a camera that can quickly pay for itself and is ready to shoot out of the box, grab the C100 Mark II for $4500.
Have an opinion on one or both of these cameras? I'd love to hear it. Hate Canon and love Sony? I don't really care. Think the BlackMagic Ursa Mini 4.6k is the next great camera for low budget filmmakers - I may agree, but it will cost you quite a bit more than a C100 Mark II. Thinking of buying a C300MarkII for 16 grand? You're out of your fucking mind. Waiting for NAB 2016 in a few weeks? Not a bad idea.
WANT THE FILM LOOK WITH YOUR C100 MARK II? Check this article --> http://bit.ly/2loeQ5V