DLog & HLG

[Ralph thompson]

There has been some discussion already on the difference between HLG and DLog capture on the M3 & M3Classic. I am not well educated in video technology but was a bit confused by some of the discussions around DLog & HLG so I did my own comparison, looking at the Metadata. In conclusion, there's no doubt in my mind now that HLG delivers a better quality video (all else being equal) with HLG providing more potential in post than DLog (and less work). This assumes that you do post processing, which for me, is always. I've never live streamed. In the attached meta dumps, the LHS is DLog and RHS HLG (they are otherwise identical ~7 sec, H.265, CBR, 30FPS, 5K etc). My interpretation is that the camera capture is identical in both modes but the processing of the clip is where the difference lies. They both start as 10 bit 4:2:0 with the same bit rate. But then things diverge with DLog being contained in BT.709 (8 bit) and HLG contained in BT2020 with a wider 10 bit colour gamut. Clearly HLG has more potential provided you let your SW know you're working with BT2020.
I don't understand the "Other" and "Other #2" folders, why one says Bit Rate mode Variable and the other says Bit Rate Constant, since the camera setting was CBR.

 

[DougMcC]

I will be watching so I can learn. Thanks for posting.

 

[brett8883]

There has been some discussion already on the difference between HLG and DLog capture on the M3 & M3Classic. I am not well educated in video technology but was a bit confused by some of the discussions around DLog & HLG so I did my own comparison, looking at the Metadata. In conclusion, there's no doubt in my mind now that HLG delivers a better quality video (all else being equal) with HLG providing more potential in post than DLog (and less work). This assumes that you do post processing, which for me, is always. I've never live streamed. In the attached meta dumps, the LHS is DLog and RHS HLG (they are otherwise identical ~7 sec, H.265, CBR, 30FPS, 5K etc). My interpretation is that the camera capture is identical in both modes but the processing of the clip is where the difference lies. They both start as 10 bit 4:2:0 with the same bit rate. But then things diverge with DLog being contained in BT.709 (8 bit) and HLG contained in BT2020 with a wider 10 bit colour gamut. Clearly HLG has more potential provided you let your SW know you're working with BT2020.
I don't understand the "Other" and "Other #2" folders, why one says Bit Rate mode Variable and the other says Bit Rate Constant, since the camera setting was CBR.

It clearly says in your metadata that the D-log is 10 bit. Also, D-log by definition is not rec 709. The colorspace for D-log is called D-gamut but since D-gamut isn’t a standard delivery colorspace meant to be played as a final product in a video player the colorspace information isn’t in the metadata or at least isn’t recognized by your metadata reader and reverts to treating it like rec 709.

In contrast the HLG is a delivery color space and gamma. The metadata identifying it as HLG is what allows it to be played in HDR on HDR displays straight out of camera which is the main advantage to shooting in HLG. HLG is also a standardized colorspace and gamma so it is easy to convert from HLG to any other colorspace.

It’s perfectly reasonable to prefer working with HLG over D-log it’s just that the reasons you are giving for that opinion don’t make any kind of sense and a lack of understanding is apparent. Not trying to put you down, we all start somewhere but I’d encourage you to continue your studies on the subject and gain more experience before coming to this kind of conclusion. Hopefully you get to a place where you understand the merits of both methods even if you strongly prefer one over the other. To try and prove that one is quantitatively better than the other is like trying to prove quantitatively that red is a superior color to blue.

 

[brett8883]

You are correct that the processing is different though

 

[manowar_gub]

I agree with brett8883 in terms of deep understanding what profiles are, also as log profiles usually tagged as rec709 to made them reviewable

personally for me, d-log of my a2s look having minimal post-process comparing to HLG profile (at least it have extra sharpness)

could you, Ralph thompson, upload original files of each profiles, in different scenes, especially with high DR (bright sky + dark shadows)? 10 sec length for each vid is enough

 

[Skyscope]

HLG is a compromise. It's designed to deliver some kind of easy tu use (Low Level) HDR from aquisition (camera) to delivery (HDR-TVs), and to be at least somewhere compatible with SDR-TVs. It's not meant to be color-graded or manipulated somewhere in the pipeline.
And if you do, it gets tricky, because HLG has a linear gamma curve (like Rec.709) up to 70%, from there it uses logarithmic gamma like Log. That makes grading and shot matching with several shots or cameras very complicated.
You get most dynamic range with D-Log. Log can easily be transferred to HLG in Post, but not vice versa without loosing information.

Thats' for gamma. Colors are another strory, because HLG uses Rec.2020 Color Space, which has to be transfered to Rec.709 for standard SDR-Diplays, otherwise colors are shifting intensely. Take two clips, one in HLG and one in Normal and compare the Reds for example.
But if you start to transfer HLG color spaces in Post, you can directly use D-Log in your workflow.

 

[Ralph thompson]

I respect your feedback Skyscope, thank you. I've found HLG very easy to work with in post and no difficulty fitting M3Classic HLG in with BMPCC4K BRAW and other lower quality media. I appreciate we maybe work in different environments, you maybe in a more demanding industry. Having used DLog with M2P and now with the M3Classic, I find it a lot of work to match DLog with other clips and as has been said in other posts, its not clear that DLog is true 10bit, at least rec 709 limits the colour profile. But I appreciate it's not raw so it's bound to be more limiting than RAW. DJI "captains" seem to be evasive on the DJI forum and I haven't seen any direct response from DJI. The clarity and dynamic range that comes with HLG I find impressive. I find HLG has plenty of room in post (recognizing that its not RAW) to reclaim highlights and pull out shadows and has relatively low noise (one comparison on YouTube showed lower noise in HLG that ProRes). I've had lots of experience with Davinci Resolve Studio and feel the HLG provides the best starting point for colour grading. Thanks again for your feedback.

 

[Skyscope]

Having used DLog with M2P and now with the M3Classic, I find it a lot of work to match DLog with other clips and as has been said in other posts, its not clear that DLog is true 10bit, at least rec 709 limits the colour profile.

Rec.709 defines Gamma and Gamut / Color Space, not Bit Depth.
And D-Log is definitely 10 bit with the Mavic 3, as it was with the Mavic 2 Pro. You can check this easily by yourself by manipulating a sky gradient, as I did with the Mini 3 Pro, when I was the first to discover it has 10 Bit Color in D-Cinelike.

With the Mavic 3 D-Log is highly improved compared to D-Log M of the Mavic 2 Pro. And it's very simple to transfer it to SDR or even HDR, because the Mavic 3's D-Log is nearly the same Gamma (and Gamut/Color Space) as SLog3 / SGamut3.cine from Sony Cameras. You can for example simply use SLog3 LUTs with the Mavic 3 to get a nearly perfect Transfer.

I find HLG has plenty of room in post (recognizing that its not RAW) to reclaim highlights and pull out shadows

You are right that HLG has more lattitude in highlight areas than the Normal-Profile (not D-Log), but not in the Shadows. It's not possible, because HLG and Normal (Rec.709) are sharing the same Gamma-Curve until IRE 70. ("Hybrid Log Gamma", because of it's linear component until IRE 70)

D-Log (or any Log) is simply another story than HLG, there is no way around it. Because we don't get RAW in Video with the Mavic 3, It's the greatest common denominator with the most information and colors possible. Like I said, you can transfer D-Log easily to any other HDR, even HLG.

But if you can get your desired results in HLG and you are comfortable with your workflows, then of course keep it that way. But in your own interest be open minded and perhaps give D-Log another try in high demanding conditions regarding dynamic range.

 

[Ralph thompson]

Thanks Skyscope. I will give dlog another try, I’m still learning with the M3Classic. I’d understood that the dlog in M2P & M3 were similar. I may have been confused by the metadata which showed dlog in rec 709 (this maybe a misinterpretation on the data) a smaller colour space which does have to be 8 or 10 bit depth whereas HLG is rec 2020, a much broader colour space requiring 10bit colour depth. But as I said at the start, I’m not a video expert, my background is still photography.
thanks again.

 

[Skyscope]

I’d understood that the dlog in M2P & M3 were similar.

No, they are very very different. But both with 10 bit color depth.

HLG is rec 2020, a much broader colour space requiring 10bit colour depth.

Not really. D-Gamut is broader.

 

[Ralph thompson]

Although not deeply analytical, I’m just comparing dlog and hlg video of macbeth color checker & other test cards. I have to admit dlog does look good. I see DaVinci Resolve v18 has a DJI Mavic 3 dlog to rec 709 LUT and DJI D gamut color space. May have to swoll my pride here
Thanks