PQ ≠ HDR10 ≠ BT.2100

Yesterday I looked at a few SDR slides from “Practical HDR and Wide Color Techniques in Gran Turismo SPORT [1]” and pointed out places where color gamut, OETFs/EOTFs, and application standards had become conflated. The HDR section of the presentation exhibits a similar pattern, this time treating HDR formats, transfer functions, and complete television-system recommendations as though they were interchangeable.

For example, this bullet:

• HDR10, PQ, Dolby, ITU-R BT.2100 • Same Curve, different name.

isn’t just imprecise—it collapses several different layers:

• HDR10 is an HDR format. 
• PQ is a transfer function.
• Dolby Vision is an HDR format/ecosystem, not a transfer function.
• ITU-R BT.2100 is a complete television system recommendation defining HDR television, including both PQ and HLG transfer functions, colorimetry, signal formats, etc.

Those are simply not “different names for the same curve.”

Note: The slide says:

“HDR10, PQ, Dolby, ITU-T BT.2100”

That should be ITU-R BT.2100, not ITU-T.

ITU-T and ITU-R are completely different sectors of the ITU.

Likewise, on the next slide:

“ITU-R Recommendation BT.2100 HDR10 EOTF” = ST2084 = PQ Curve

That’s problematic in several ways.

More accurately:

ST 2084

      ↓

defines

      ↓

PQ EOTF

      ↓

adopted by

      ↓

HDR10

      ↓

specified within

      ↓

BT.2100

rather than

“ITU-R BT.2100 HDR10 EOTF” = ST2084 = PQ

These aren’t isolated factual mistakes—they reveal a pattern in the way the material is presented. In both the SDR and HDR sections, the presentation tends to flatten a layered system into equivalences:

• color space = gamut = standard
• OETF = EOTF = gamma
• PQ = HDR10 = Dolby Vision = BT.2100

If someone already thinks that “gamma” can refer interchangeably to an OETF, an EOTF, or a display power law, then introducing PQ, HLG, HDR10, and BT.2100 only compounds the confusion. HDR is much easier to understand once the SDR fundamentals are disentangled.

1. Hajime UCHIMURA, Kentaro SUZUKI, “Practical HDR and Wide Color Techniques in Gran Turismo SPORT,” SIGGRAPH ASIA 2018, Polyphony Digital Inc. 

Gamma ≠ Gamut ≠ EOTF