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.
