GH5 nick driftwood on Hyper Log Gamma - HLG - interesting!
- Thread starter robfilms
- Start date
Yeah, HLG looks like it will become one of the best quick delivery formats for HDR playback. I have to upgrade my production monitors and my home TV set to HDR in order to take advantage of this new format. It's an exotic format right now, but I could see it becoming the norm within the next 2 years.
Bassman2003
Veteran
Very cool. Great looking images.
Cary Knoop
Veteran
There are, and there likely will remain, alternatives to HLG.
The best strategy is to capture in V-Log L and render to the "whims of the day".
The best strategy is to capture in V-Log L and render to the "whims of the day".
...But the whole idea of HLG is to have footage that is pretty much ready to go with little to no color or contrast changes in post, so it's a fast turn around format. V-LOG L is the format you shoot when you can afford the time to properly deal with it in post.
Cary Knoop
Veteran
Right, but what if HDR10 or Dolby Vision or yet some other new format takes off?
If you record V-Log L you can convert to any of those at any time.
I'd keep the baking for later!
I'm sure that HDR10 and Dolby Vision will be popular, but I can also see clients asking specifically for HLG footage so they can start prepping it for broadcast as soon as you drop your footage off. No time for any type of baking.
Thomas Smet
Veteran
Pretty sure HLG was designed to be a consumer format so one could shoot HDR of their kids soccer game on the GH5 and hook the camera up to their fancy new 4k TV and watch it in HDR with no extra effort involved at all. It is a baked in profile to use as is out of the box.
If one is a professional who will edit and grade the material and potentially deliver to different users then yes without a doubt shooting V-log is the better choice so you can deliver to just about any color space you want to. If one wants to shoot HDR and watch HDR with little to no touching of the material than HLG is the way to go.
I'm not entirely sure if/when clients would ask specifically for HLG. Seems like wishful thinking right now considering how little clients actually know about video in general. I personally would treat HLG right now as a shoot/watch format for family stuff with a little extra range without the extra hassle.
If one is a professional who will edit and grade the material and potentially deliver to different users then yes without a doubt shooting V-log is the better choice so you can deliver to just about any color space you want to. If one wants to shoot HDR and watch HDR with little to no touching of the material than HLG is the way to go.
I'm not entirely sure if/when clients would ask specifically for HLG. Seems like wishful thinking right now considering how little clients actually know about video in general. I personally would treat HLG right now as a shoot/watch format for family stuff with a little extra range without the extra hassle.
From what I've read online the HLG format was originally cooked up by the BBC and NHK as a 4K HDR broadcast transmission format. One of the main problems they were trying to solve was re-syncing dropped transmissions, as previous formats did not support frame accurate video/audio sync in a single stream. So HLG is definitely going to be used as a streaming format for 4K HDR TV broadcasts.
I could see HLG used any time you need fast turn around HDR video, like news or sports segments. HLG definitely looks way better than SDR video when viewed on a HDR TV set, so in a few years time when a significant portion of the viewing audience owns HDR TV sets they are going to want to see HDR content instead of SDR content, and HLG will fit right in as a quick'n'dirty HDR format.
HLG is not baked-in. It's a scene-referred color space, and in that respect, the same as V-Log. The difference is that HLG is a standard that can be fed directly to a TV, whereas V-Log is proprietary and no TV can display it directly.
HLG starts with a conventional 2.2 gamma curve for the lower 1/2, and tacks on a log gamma curve for the upper half. HLG can accommodate 17.6 stops of DR. The advantage to HLG is that it uses no metadata, making it broadcast friendly with existing infrastructure, meaning more available content, and live programming for us all. HDR10 currently needs separate grades for SDR and HDR copies while DV requires separate grades called 'trim passes' to generate the metadata that differentiates the base layer from the enhanced layer. Additionally, DV tone maps to specific licensed display products, requiring additional metadata generated from trim passes. Finally, DV and soon HDR10 will make possible scene by scene or even frame by frame dynamic metadata; more metadata necessitated because a very bright or very dark scene will cause out-of-gamut values when going from the larger HDR space to the smaller SDR space. The larger space of HDR is described as 'color volume' which if you think about it 3 dimensionally with color gamut (2020) on the x-y axis and luma on the z axis, the color volume is x times y times z. The color volume of HDR (chroma times gamma) is much larger than SDR.
Do we really need all this metadata? Well if you are Dolby you do because they want to license their technology to as many display makers as possible, including many that can't meet their own minimum display targeted color volume, and thus are tone mapped to the capability of the display with metadata spawned by a trim pass during the production stage. It's custom, but is this practical? It appears to be the case for cinema that it is, and for UHD Blu-ray as well although the latter are required to support HDR10 as the standard.
HDR10 is the license free part of Dolby Vision called the EOTF ST-2084; electro optical transfer function, the essence of display referenced video. The gamma transfer references a specific brightness level for each part of the frame that is absolute cd/m^2 or 'nits'. A DV licensed display that can't meet the color volume needs to be tone mapped into the color volume it has.
DV is very tedious to grade because each exception to the display referenced EOTF needs metadata from a trim pass. At the end, you create a mezzanine file that has to be handed off to a production house. HDR10 is somewhat easier since you don't need the last step.
HLG on the other hand, is not display referenced brightness, it is scene referenced gamma which has another advantage that the consumer retains control of his picture controls, brightness, contrast etc. That's important in my opinion, because although we all respect 'director's intent' the concept loses some relevance once the content leaves the controlled setting of the motion picture cinema, and where some people will want to watch in a bright room, others in a dark room. These are beyond the control of the director but very irritating to the consumer if he has complaints about the picture being too dark or too bright.
HLG solves all these problems being metadata-free, broadcast friendly, easy to grade, adjustable on any tv and backward compatible.
This is my opinion when I say this, and not a knock on Dolby Labs who invented HDR and the EOTF ST2084 and made it available for free to everyone, but the main reason for the existence of the DV features of tone mapping, dynamic metadata is to protect the brand by licensing Dolby products. Nothing wrong with that at all. But it complicates matters for content producers having to grade all those trim passes. HLG has 95% of the benefit with none of the drawbacks, and was a great proposition put forward by BBC and NHK.
Do we really need all this metadata? Well if you are Dolby you do because they want to license their technology to as many display makers as possible, including many that can't meet their own minimum display targeted color volume, and thus are tone mapped to the capability of the display with metadata spawned by a trim pass during the production stage. It's custom, but is this practical? It appears to be the case for cinema that it is, and for UHD Blu-ray as well although the latter are required to support HDR10 as the standard.
HDR10 is the license free part of Dolby Vision called the EOTF ST-2084; electro optical transfer function, the essence of display referenced video. The gamma transfer references a specific brightness level for each part of the frame that is absolute cd/m^2 or 'nits'. A DV licensed display that can't meet the color volume needs to be tone mapped into the color volume it has.
DV is very tedious to grade because each exception to the display referenced EOTF needs metadata from a trim pass. At the end, you create a mezzanine file that has to be handed off to a production house. HDR10 is somewhat easier since you don't need the last step.
HLG on the other hand, is not display referenced brightness, it is scene referenced gamma which has another advantage that the consumer retains control of his picture controls, brightness, contrast etc. That's important in my opinion, because although we all respect 'director's intent' the concept loses some relevance once the content leaves the controlled setting of the motion picture cinema, and where some people will want to watch in a bright room, others in a dark room. These are beyond the control of the director but very irritating to the consumer if he has complaints about the picture being too dark or too bright.
HLG solves all these problems being metadata-free, broadcast friendly, easy to grade, adjustable on any tv and backward compatible.
This is my opinion when I say this, and not a knock on Dolby Labs who invented HDR and the EOTF ST2084 and made it available for free to everyone, but the main reason for the existence of the DV features of tone mapping, dynamic metadata is to protect the brand by licensing Dolby products. Nothing wrong with that at all. But it complicates matters for content producers having to grade all those trim passes. HLG has 95% of the benefit with none of the drawbacks, and was a great proposition put forward by BBC and NHK.
The BBC touts HLG's backwards compatibility, but the only TVs it's backwards compatible with are BT.2020 SDR displays. There aren't so many of those, and no consumer-friendly delivery mechanism exists for BT.2020. So HLG's backwards compatibility with BT.2020 is almost entirely irrelevant. For all practical purposes, HLG is a brand new format that needs conversion for common SDR displays.