HLG explained

[kye]

Great video talking about HLG

Talks about HLG acquisition, HLG delivery, backwards compatibility, grading, 709 conversions, exposure, HDR10, the HLG curve, cine gammas and commercial opportunities.

[Mako Sports]

Alister is the man

[Grimor]

Interesting talk about recovering 2 stops of burning highlights...

[kye]

14 hours ago, Grimor said:

Interesting talk about recovering 2 stops of burning highlights...

Well, he makes no sense through most of that video but was absolutely right about one thing - when he said "I don't know the technicalities of what's actually going on".

My understanding would be this:

• HLG includes the whole DR of the camera and the other profiles he tested don't
• FCPX is confusing him..  here's what I think is happening:
  • FCPX takes the HLG file (which isn't clipping anything) and then converts it automatically to rec709, "clipping" it heavily but retaining that data in super-whites
  • When he makes adjustments to lower the exposure those values above 100 get brought back into range
  • He thinks that FCPX pushing the exposure beyond 100 somehow means the GH5 "clipped" (it didn't)
  • He things that lowering the exposure in FCPX and getting the highlights back means you can somehow recover clipped highlights (you can't)
• If something is clipped then the values are lost (digital clipping is data loss)
• FCPX is "helping" by automatically doing things without asking you

TL;DR - HLG has greater DR; exposing for HLG is different than rec709; FCPX is "helping" and confusing people; and this guy isn't the person to be listening to for this stuff.

[thephoenix]

and there's nothing exectional in recovering 2 stops of highlights, but hey this is youtube, everything has to be insane ?

[kye]

20 minutes ago, thephoenix said:

and there's nothing exectional in recovering 2 stops of highlights, but hey this is youtube, everything has to be insane ?

Actually, I think that it's a deeper issue.  

Just look at the terminology - "recovering highlights" is something that you do when things have gone brighter than white.  This only makes sense if white has a shared definition, which it does if everyone is publishing in rec709.  

HLG is actually a delivery standard, so when someone shoots in HLG and are going to deliver in HLG then there is no recovery - if the camera clips the HLG file then that data is clipped.  Same as if you shoot rec709 for delivery in rec709.  If this guy was talking about filming in LOG then no-one would assume that he's delivering in LOG, so the conversation would be in the context of the default and standard delivery colour space / gamma.

The point of HLG is that it's an alternative to rec709, and so now there is no default / standard / goes-without-saying reference point.

Edit: coming from a camera, clipped HLG is the same as clipped 709..  that is some cameras may not actually be clipped because they might include super-whites in the output file, like I know the Canon cinema cameras do (as well as others I'm sure).  Ah, I love the smell of confusion in the morning.

[thephoenix]

my point was to say that even in flog you can recover 2 stops of hi exposure, actually it depends more on your camera's sensor and it's dr.

just to say that there are tons of shi... video on youtube where everything is "insane" just to get audience and full of craps

[thebrothersthre3]

Well his point that it holds dynamic range better than the other profiles is true. But yeah I kye is right he's confused by the HLG looking clip in FCPX

[mirekti]

HLG makes sense to me. For example a football match and half the field is in shade, the other lit by Sun. With SDR we can have on or the other exposed ok and that's it. 

HDR itself, well, that's something I really don't understand. I mean, we had HDR photos way before video, and some well processed looked gorgeous on SDR monitors. Why the heck I need 1000 nits or more in a display, a day on the beach perhaps?  
I am still to be convinced this HDR is the way to go, and not a marketing scheme like 3D (it obviously is, and that's what market dictates), but I am perfectly fine with 6-7 stops.
Don't get me wrong, I do want a camera with more dynamic range, but only so I could be able to map it to those 6-7 stops. So SDR, with wider gamut for better colors pulled from let's say 16 stops camera and BT.2020, that's it. 

Example, look at some lit part of the room but not too bright, and then look somewhere where it is darker. Your eyes almost instantly adapt, open aperture for that darker scene and start noticing things. The more the stops between the lighter and darker area the more time it takes for the eyes to adjust. 
My question: How will HDR do that? No way, the image has to be withing certain dynamic range so our eyes can look at it at once. Not sure how much, but event these 6 stops we have right now make LCD black which is not black truly black in our head. The second thing, the area of a display is a too small area for our eyes to behave dynamically. 

 Great video, btw. :D

 

 

[Mako Sports]

6 minutes ago, mirekti said:

HLG makes sense to me. For example a football match and half the field is in shade, the other lit by Sun. With SDR we can have on or the other exposed ok and that's it. 

To someone like me that shoots events, mainly sports this is exactly why I love HLG. Stock profiles give me crunchy highlights and in my sector no one has time to grade log. 

[KnightsFan]

@mirekti HDR just means that your display is capable of showing brighter and darker parts of the same image at the same time. It doesnt mean every video made for an HDR screen needs to have 16 stops of DR, it just means that the display standard and technology is not the limiting factor for what the artist/creator wants to show.