First impressions of the C100 Mark II
Image quality
From my short experience with the Mark II I can say that the image quality has slightly improved over the original C100. Noise performance is better for sure, with the Mark II showing less noise at every equivalent ISO. The noise structure is also much finer, less flaky. There also seems to be a slight improvement in detail. I can't really comment on moiré/aliasing, because the original C100 had virtually none. Rolling shutter is exactly the same. All in all, the image quality improvements are so small that I can't imagine it being a decisive factor to choose one camera over the other. That OLED screen...
What really sets these two cameras apart is the OLED display on the Mark II. It is a lovely detailed screen, with vivid and accurate colors. On the original C100 I was always pleasantly surprised when I reviewed the footage I had shot, because it looked so much better then when shooting it. Now, I wonder how I could even use such a low-res LCD for focussing! The new OLED is such a joy to use, and makes judging focus, exposure and color much much easier. I even found myself having much less need for focus peaking, that's how crisp the display is!
EVF
The EVF on the Mark II is now actually usable. Compared to the miniscule peeking hole on the original C100, we now get a luxurious tiltable EVF with a pretty good screen. The screen in the EVF is large, but not so big that you have to scan around. I did have to make some adjustments to the brightness and contrast settings of the EVF, as by default the image looks a bit dull. The large eyecup does a great job of keeping out external light, even when wearing glasses. 50P/60P
By now, it seems like someone at Canon watched all the C100 reviews, took notes, and sent them to the design department, as Canon fixed all major complaints about the original C100. Philip Blooms passionate plea "Don't take away my slow motion" is certainly one of them, as we now have 50P and 60P framerates. From my tests, the image is only slightly less detailed than 25P (hardly noticable). I also found it quite convenient to have the option of doing the slow-motion conversion in-camera, as you can immediately see the result of what you did, and when mixing slow motion with realltime shots in the edit, it saves a lot of work too.
Dual Pixel AF
Autofocus isn't among my first priorities when looking at a large sensor interchangeable lens camera, but after a little testing must say I'm impressed by its speed aand accuracy. I can see it coming in handy in walking interview type situations where the distance to your subject varies greatly. When used in conjunction with the perfectly placed AF-lock button, the Dual Pixel can also be used to quickly grab focus, lock it, reframe, and start shooting. I do find it a shame that the focus square cannot be repositioned to either side of the frame, as I seldomly make shots where the subject is in the center of the frame. Other improvements
Futhermore Canon added loads of refinements that make the camera a lot easier to use in the field: a real EVF (nothing like the stub on the original C100), scopes and much better button placement. Though nothing groundbreaking, together these small improvements all add up to a more enjoyable and faster experience. When doing these comparison tests, I soon found myself fumbling with the controls on the original C100 (a camera I have used extensively), while on the Mark II everything was easy to find and fast to adjust. And then that screen...
Conclusion
While the updates to the Mark II might seem far from groundbreaking at first, I found these small changes matter a whole deal in my level of confidence in working with the camera. On the original C100 I was constantly toggling between focus assist modes, just because the screen didn't give me that confirmation. On the Mark II I find myself hardly needing those tools. White balance on the original C100 always seemed a lot cooler than what I was actually recording, while on the Mark II it is spot on. Colors and exposure are also more accurate, giving me a much better impression of the image I am actually recording. The vastly improved screen alone turns it into a totally different camera to work with.
If you need 4K or 120fps for your projects, this is clearly not the right camera for you, but if you're doing any kind of broadcast-, documentary- or fast-paced fiction work, the updated version of the camera fixes everything that sometimes made the camera harder to work with. If you're looking for a lightweight camera, with great ergonomics, superb audio-capabilities, built-in ND's, flexible rigging and now one of the nicest screens available, be sure to consider the C100 Mark II.
Is the Mark II worth the premium over the original C100? I guess you already know my answer to that...