V-Log internal is worse than the originally built-in Natural picture profile. V-Log introduces banding. It brings up the shadows quite a lot and helps to get more consisyent results in different lighting. It truly works great for 10-bit 422 HQ external recording. However, V-Log is technically about a 7 - 80% IRE value. In other words, when you grade the footage in post, you are once again, essentially expanding your IRE back to 0-100%. Using an external recorder with LUTs built into the recording is about the only way you'll ever see the true nature of the GH4. At that point, your file sizes are massive in 4K 422 or 422 HQ.
After shooting in the GH4 for the past year, its an easy cam to work with. But it is water colors at best with just enough dynamic range to make you think "filmic." The 8-bit codec is great for Natural and Cine-D, but your pushing your luck on set not shooting Raw.
What I've learned from shooting Raw on the 5D3, 50D, 5D2, BMCC, and BMPCC is that the Canon's skin tones are so far beyond these "Shelf-Stocking" Sony sensors that finding the way into 90% of the market. The BMCC may have better Dynamic Range, but finding a beautiful "wedding look" is quite an art. The GH4 is using a Sony sensor, by the way.
When I first tested the Gh4, I sold off the 5D3 because of the easy-to-use work flow in adequate lighting... To process 4k, I've simply honed in on Open CL / Cuda Technology, Intel I7 processors, and proper cooling designs. The GH4 edits in Premiere at 1/4 res on 2012 Macbook Retinas with NVidia graphics in real-time with no issues and a couple of LUTs on top to make the grade. The 5D3 is playing back in real-time in DaVinci Resolve 12 on the same system with a couple of nodes...
The 5D has high chroma Dynamic Range while the Sony sensor's have high luminance dynamic range. Dpending upon the look, the 5D3 is going to saturate the scene with so many millions of more accurate colors. And it will look amazing. The GH4 will attempt to show you all the highs and lows and even tweak the picture profile around to make you think Canon, but you are not going to get God-Send skin tones to the client without an external recording solution. Even then, the Canon has a higher bit depth, but the GH4 is a picture-taking video camera in the sense that it's freeze frames are perfect. However, motion takes 80% of the resolution away... Another reason to shoot for colors and not for the resolution.
Taking a step back, I am shooting on BMCC MFT with a speed booster in an attempt to hit record and have it record at every turn. It's a professional solution and has been a great combo of "Skin tones / Resolution." The BMCC now has a 2x Lossless compression too. The 2400 x 1350 Raw files are smaller than the 5D3 1920x1080. I believe that its only a 12 bit readout that gets unpacked to a 16 bit color space. Perhaps that's another reason to shoot native 14-bit on the Canon?
But look at the sensor size too. The GH4 and BMCC are easier to operate because the depth of field is completely different than the 5D3. With the 5D3 you may have to work harder on focus, but when its on, I'm confident the folks on camera will appreciate being separated from other subjects.
Versatility-wise, you'll be much more flexible with a 5D3 than a GH4 and a BMCC. But, how reliable and for how long are your takes? Both the GH4 and BMCC have no recording limits and reasonable codec choices for long-term capture. A 128 GB SDXC UH3 lasts for 2hrs and 51 minutes in 4K. The BMCC in Raw blows through 1hr and 33 minutes of Raw at 480GB. In my opinion, the Canon is so versital its worth changing out cards and actually being able to record at ISO 3200 and have wonderful results.
