ISF Color Science & Image Fidelity 3 — Questions and Answers
Question 1: What does 'delta E' (ΔE) measure in display calibration?
- The difference in luminance between two measurements
- The perceptual color difference between a target and measured color (Correct answer)
- The electrical noise in a display's panel driver
- The difference in refresh rate between two display modes
Correct answer: The perceptual color difference between a target and measured color
Delta E quantifies the perceptual difference between two colors; a ΔE of 1.0 is considered the just-noticeable difference threshold for trained observers.
Question 2: In CIELAB color space, what does the 'L*' axis represent?
- Chroma saturation from neutral to vivid
- Hue angle from 0° to 360°
- Perceptual lightness from 0 (black) to 100 (white) (Correct answer)
- Luminance in candelas per square meter
Correct answer: Perceptual lightness from 0 (black) to 100 (white)
L* in CIELAB represents perceptual lightness on a scale of 0 (absolute black) to 100 (perfect diffuse white), designed to be perceptually uniform.
Question 3: Which HDR standard specifies a peak luminance of 10,000 nits as its reference maximum?
- HDR10
- Dolby Vision
- HLG
- PQ (SMPTE ST 2084) (Correct answer)
Correct answer: PQ (SMPTE ST 2084)
SMPTE ST 2084 (Perceptual Quantizer / PQ) defines its electro-optical transfer function with reference to a 10,000 nit absolute peak luminance ceiling.
Question 4: What is the primary visual artifact caused by insufficient bit depth in a gradient, commonly seen in smooth sky gradients?
- Aliasing
- Posterization (banding) (Correct answer)
- Chromatic aberration
- Motion blur
Correct answer: Posterization (banding)
Posterization or banding occurs when insufficient bit depth creates visible steps in a smooth gradient instead of a continuous tonal transition.
Question 5: What is the purpose of dithering in display signal processing?
- To increase perceived frame rate through motion interpolation
- To simulate higher bit depth by randomizing quantization error across pixels (Correct answer)
- To reduce power consumption on OLED panels
- To sharpen edge detail in compressed video
Correct answer: To simulate higher bit depth by randomizing quantization error across pixels
Dithering adds controlled noise to quantization errors, spreading them spatially so the eye integrates them into smoother perceived gradients.
Question 6: When calibrating a display to Rec. 709 color primaries, which set of primary chromaticities defines the standard?
- R(0.640, 0.330), G(0.300, 0.600), B(0.150, 0.060) (Correct answer)
- R(0.708, 0.292), G(0.170, 0.797), B(0.131, 0.046)
- R(0.735, 0.265), G(0.274, 0.717), B(0.167, 0.009)
- R(0.680, 0.320), G(0.265, 0.690), B(0.150, 0.070)
Correct answer: R(0.640, 0.330), G(0.300, 0.600), B(0.150, 0.060)
Rec. 709 defines its color primaries at R(0.640, 0.330), G(0.300, 0.600), B(0.150, 0.060) in CIE xy chromaticity coordinates.
Question 7: What phenomenon causes a display's perceived black level to appear elevated when measuring in a dark room?
- Temporal dithering overflow
- Light leakage or backlight bleed in LCD panels (Correct answer)
- Voltage overshoot in response time settings
- Gamma mismatch between source and display
Correct answer: Light leakage or backlight bleed in LCD panels
LCD panels cannot completely block backlight in dark areas, causing light bleed that raises the minimum measurable luminance above true zero.
ISF Color Science & Image Fidelity 3
What does 'delta E' (ΔE) measure in display calibration?