SimplePanda
Second Officer
Flight distance : 1719062 ft
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I really don't think it's the 60Mbps bitrate that causes D-Log troubles. It certainly is low for 4K, but the P4/X3/X5 struggle with D-Log even at 1080p.
Case in point, I have (and have worked with) quite a few AVCHD cameras over the years now, all of which are shooting 1080p24 to 24Mbps H.264 and they get excellent results (The Canon C100, for example, simply blows away the P4/X3/X5 in recorded video quality even with similar quality lenses).
I think where you're really going to run into issues with D-Log is that, fundamentally, you're talking about trying to post-grade 8-bit 4:2:0 footage. No matter what camera, that's always going to have fairly limited headroom. DJI is advertising 13 stops of dynamic range on X5. With 8 bits, you have a (not so) whopping 18 gradient points per stop on a linear curve. That's not a lot of data to work with and you're always going to be fairly limited in your grading abilities as a result.
It's not that simple of course - the LOG curve itself changes how much data per stop you get, adding variability based on where the camera is designed to perform well in LOG profile.
HOWEVER, the bigger issue I think is that D-Log seems to have actually changed earlier this year. My guess is that they optimized it for X5R rather than creating a D-Log Raw curve as a separate entity.
If you go here:
http://www.dji.com/zenmuse-x5/info#downloads
Download the sRGB LUT pack from DJI. Within that you're going to find:
DJI_X5_DLOG2sRGB.cube
DJI_X5_DLOG2sRGB_before20160401Firmware.cube
So DJI is providing a LUT that for pre-April. This happens all the time with other camera vendors (Blackmagic has multiple versions of their BMDFilm LUTs for Cinema Camera, for example) but it typically happens as a way to improve the LUT performance. My guess (and it's just a guess) is that the "before 20160401" curve that DJI provides isn't an improved LUT for D-Log footage so much as it's a LUT for footage shot on firmware BEFORE 20160401 - suggesting the D-Log curve changed back in April.
This implies you can simply use the new LUT as a basis for where D-Log performs well with current firmware - but it's not that simple in practice. Really, it feels like DJI kinda broke D-Log for their 8-bit encoding cameras in favour of their RAW camera and the current LUT simply tries to mask that as much as possible. That really doesn't help you if you're not using their LUT and are just grading the footage directly (as many will be doing) - you have to work with the (seemingly broken) new curve.
Just my guess.
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