Unified HDR Reference White - VideoQ Proposal
What is the problem & the opportunity?
The advent of HDR and Wide Color Gamut technology means change to custom and practice. New workflow rules must be established and honed.
The problem is that in this early adoption phase, competing standards are anything but unified. This present the industry an opportunity to establish an agreed upon commonality between the current incompatible array of standards and self interest.
The solution to harmonious, technically correct and agile content production through to distribution is proposed in the form of an HDR Reference White standard.
In the case of measurement of the HDR video content Light Levels the use of cd/sq.m should be avoided; instead we should use different units – ‘video content LL nits’ and/or ‘video content LL percents’ based on calculation of LL = EOTF(max(R,G,B)) values.
Light Level value can be mapped to or replaced by Relative Data Level in percents and/or Absolute Data Level, e.g. 10 bit maxRGB value.
A group of the renown industry experts proposed new Unified HDR Reference White values equally suitable for PQ and HLG systems
For PQ & HLG, optical "Diffuse White" and computer graphics cases we proposes practically useful "easy" round figures.
The proposed Unified HDR Reference White Levels are:
• 75% of HLG Data Range, Relative LL 20% and 10 bit value 721 (or 720 for 8 bit 180 x4),
• 58% of PQ Data Range, Absolute LL 200 nit, Relative LL 2.0% and 10 bit value 572.For the HLG 1000 nit display case both HLG and PQ values correspond to the same 200 nit Video Content Absolute Light Level.
Benefits and advantages of the proposed solution:
• 200 nit level is close to the middle point of the typical White Levels range currently used in PQ production; this range is reported to be about 145 .. 250 nit.
• 200 nit level is safely below 300 nit, often quoted as a typical White Level of SDR content displayed by consumer grade HDR displays, and effective peak level of typical computer monitors and smartphones.
• The proposed HLG & PQ Reference White does not rely on any particular display type or display gamma.
The 1000 nit TDMB value is used only for HLG level scaling purposes, NOT as a target HLG device specification.