@Paglez J-Log (with 4:2:2 color) is what the GH4's V-Log-L should have been, but so far no LUT's or technical docs have been provided to make full use of it. If you're willing to roll your own LUT, J-Log will give you the broadest dynamic range from the LS300, so long as your lighting isn't too extreme. If you want the best in-camera results in difficult lighting, Rec. 709 with custom gamma and black level is the way to go. Both J-Log and Rec. 709 produce realistic colors; "Cinema Gamma" not so much.

@paglez J-Log is a bit of a paradox. It works only in manual exposure mode, but provides no other adjustable controls except white balance. That makes it quick to dial in, but not very adaptable to extreme lighting conditions. On the LS300, J-Log records 0% black at 7.5 IRE and 100% white at 100 IRE, with superwhites up to 108 IRE. If you set Zebra Bottom at 100%, you can use it to keep your J-Log exposure within Rec. 709 legal limits, allowing you to monitor and review the footage directly via HDMI into an HDTV. But since it doesn't use a Rec. 709 gamma curve, shadows will be bright and contrast low, so you'll need to grade it as I did with the clips above. (The built-in LUT only works in-camera.) Sharpness must also be adjusted in post, as it cannot be controlled in-camera in J-Log mode.

J-Log is excellent with controlled lighting, but in sunlight or harsh indoor lighting, J-Log forces you to either clip the brightest highlights or underexpose the midtones and shadows. With the LS300's Rec. 709 gamma curve, I can compress the highlights with the adjustable highlight knee, and boost the mids and shadows as needed with adjustable gamma and black level controls. Sharpness can also be dialed in, or turned off completely. That provides a lot more flexibility than J-Log, but requires careful preparation and evaluation with an external monitor. With J-Log, all controls are preset, so once you've set exposure and white balance, you're ready to shoot.

JVC LS300 J-Log1 test footage showing highlight interaction with several complexion types. Recorded in 1080p30 at ISO 400 with internal 50Mbps H.264 encoder in 8-bit 4:2:2 color depth. Sunlit highlights intentionally blown out to reveal highlight coloration. Graded with custom LUT and sharpened with Neat Video using zero noise reduction. The slow pan stresses the encoder to expose any motion artifacts.

Has anyone tested this camera out since the firmware update? I'd love to see how footage looks with some Voigtlanders on it.

JVC GY-LS300 firmware 2.0 update has been released, available here:

http://pro.jvc.com/pro/attributes/CAMERA/soft/gyls300_firmware_v2.0.html

Version 2.0 brings significant new features and performance upgrades to JVC's Super 35 4KCAM Camcorder:

JVC Log Gamma
Prime Zoom (allows zooming with prime lens)
Cinema 4K (4096 x 2160) and Cinema 2K (2048 x 1080) recording at true 24p
Histogram
Spot meter
Color matrix / Black Paint adjustment
4K recording at 70 Mbps
Zixi variable bitrate streaming
FTP resume function

Thinking about getting this camera. Is it Rolling or Global shutter, and if it's rolling how bad?

Nice roll-off highlights with j-log1. Seems to grade very well. Dynamic range (12 stops) seems to be in the same ballpark than GH4 with Log

this camera is amazing!

" It could have been a great camera with a better sensor, IMHO."

If it had better low light performance, I would have bought one soon after "Hands On" at NAB instead of getting a necessary Odyssey 4k recorder for my A7s. That and the also necessary 28-135 Cine lens would have paid for it. But now, $8k later I have something better for the poor/low light indoor Videos that I make.

I have not seen a Zeiss Compact Prime Cine. What does the 50 T1.5 cost and how well does it work with the zoom function? I thought that only worked on Pany MFT zoom lens.

From JVC's press release: "With the new JVC Log mode, the GY-LS300 delivers wide latitude and high dynamic range – up to 800 percent – to rival the look of film."

Well, 800%, as I understand it, may not be that great from a DR perspective. By comparison, the Sony F5, F55 or FS7's S-Log2 claim up to 14 stops of dynamic range, which is said to be equivalent to 1300%. Sony's original S-Log delivered a dynamic range of 1000%. As such, JVC's log of 800% would appear to be rather lackluster so I wouldn't expect too much improvement. Of course, the JVC's IQ may be good enough for a wide variety of applications -- particularly when you consider it's half the price of the FS7.