HDR Color Science & Dynamic Range 2 — Questions and Answers
Question 1: Which transfer function is used by HDR10 to encode luminance values?
- PQ (Perceptual Quantizer) (Correct answer)
- HLG (Hybrid Log-Gamma)
- BT.709 gamma
- sRGB gamma
Correct answer: PQ (Perceptual Quantizer)
HDR10 uses the PQ transfer function (SMPTE ST 2084), which maps luminance perceptually to encode values up to 10,000 nits.
Question 2: What is the primary advantage of the HLG transfer function over PQ for broadcast applications?
- Higher peak luminance support
- Backward compatibility with SDR displays (Correct answer)
- Greater color gamut coverage
- Lower bit depth requirement
Correct answer: Backward compatibility with SDR displays
HLG is backward compatible with SDR displays because its lower-luminance signal portion follows a conventional gamma curve.
Question 3: In the CIE 1931 color space, what do the x and y coordinates represent?
- Luminance and saturation
- Chromaticity (hue and saturation independent of luminance) (Correct answer)
- Red and green tristimulus values
- Brightness and contrast ratio
Correct answer: Chromaticity (hue and saturation independent of luminance)
The x and y coordinates in CIE 1931 represent chromaticity — the hue and colorfulness of a color independent of its luminance.
Question 4: What does the term 'color volume' describe in the context of HDR displays?
- The total number of colors in a palette
- The combination of color gamut and luminance range a display can reproduce (Correct answer)
- The size of the ICC color profile file
- The depth of color in 3D LUTs
Correct answer: The combination of color gamut and luminance range a display can reproduce
Color volume describes the three-dimensional space defined by both the color gamut (chromaticity) and the luminance range a display can produce.
Question 5: Which bit depth is the minimum required for HDR10 content?
- 8-bit
- 10-bit (Correct answer)
- 12-bit
- 16-bit
Correct answer: 10-bit
HDR10 requires a minimum of 10-bit color depth to encode the wide tonal range without visible banding artifacts.
Question 6: What is the white point used as the reference for the BT.2020 color space?
- D50 (5000K)
- D55 (5500K)
- D65 (6500K) (Correct answer)
- D75 (7500K)
Correct answer: D65 (6500K)
BT.2020, like BT.709, uses D65 (6500K) as its reference white point for display and content mastering.
Question 7: How does the Just Noticeable Difference (JND) concept inform the design of the PQ transfer function?
- It maximizes the number of encoded values at high luminance levels
- It allocates more code values where the human eye is most sensitive to luminance changes (Correct answer)
- It ensures equal luminance steps across the entire tonal range
- It compresses shadows more aggressively than highlights
Correct answer: It allocates more code values where the human eye is most sensitive to luminance changes
The PQ curve is designed so that each code value step corresponds to approximately one JND, allocating more values where the eye is sensitive (mid-tones and dark areas).
HDR Color Science & Dynamic Range 2
Which transfer function is used by HDR10 to encode luminance values?