ISF Testing Equipment & Troubleshooting Methods 5 — Questions and Answers
Question 1: A client reports that skin tones look orange on their calibrated display but the grayscale and color checker measurements passed. What should the calibrator investigate first?
- Recalibrate the primary colors
- Check the hue and saturation of the orange-red region in the CMS or 3D LUT (Correct answer)
- Increase the blue gain
- Replace the display panel
Correct answer: Check the hue and saturation of the orange-red region in the CMS or 3D LUT
Passing primaries and grayscale does not guarantee accuracy in mixed colors like skin tones; the orange-red gamut region in the CMS or LUT should be checked for hue rotation or saturation errors.
Question 2: What does 'input lag' measure in the context of display troubleshooting?
- The time delay between a signal input and the display rendering that frame on screen (Correct answer)
- The amount of time the backlight takes to reach full brightness
- The delay between audio and video outputs
- The scan rate of the display's color sensor
Correct answer: The time delay between a signal input and the display rendering that frame on screen
Input lag is the total delay—including signal processing, scaling, and rendering—between a frame being input to the display and it appearing as light on the screen.
Question 3: A video processor is suspected of adding chroma subsampling error. Which test pattern most effectively reveals 4:2:0 chroma subsampling artifacts?
- 100% white field
- Alternating single-pixel red and white vertical stripes (chroma resolution pattern) (Correct answer)
- A swept-sine luma signal
- PLUGE sub-black bars
Correct answer: Alternating single-pixel red and white vertical stripes (chroma resolution pattern)
Single-pixel alternating colored vertical stripes expose chroma subsampling limits because 4:2:0 halves chroma resolution in both axes, smearing fine chroma detail into visible color fringing.
Question 4: When calibrating HDR content on a display supporting PQ (Perceptual Quantizer), which luminance value corresponds to diffuse white in the HDR10 standard?
- 100 nits
- 203 nits (Correct answer)
- 1000 nits
- 10,000 nits
Correct answer: 203 nits
In the HDR10/PQ system, diffuse white is standardized at 203 nits (PQ code value 58), with peak specular highlights extending up to 1000–10,000 nits.
Question 5: A projector calibration shows correct color at center but red shifts to orange at the right side of the screen. Which issue does this indicate?
- Incorrect gamma
- Optical misalignment causing lateral chromatic aberration or lens color shift (Correct answer)
- High ambient light on the right side
- Red gain set too high in the CMS
Correct answer: Optical misalignment causing lateral chromatic aberration or lens color shift
Spatially varying color errors (correct at center, shifted at edges) point to optical chromatic aberration or lens/prism misalignment rather than electronic gain or ambient light issues.
Question 6: Which calibration tool feature allows simultaneous measurement and display adjustment without repeatedly switching between devices?
- Manual patch generation
- Closed-loop or 'live' calibration mode (Correct answer)
- Log encoding
- Spectral mismatch correction
Correct answer: Closed-loop or 'live' calibration mode
Closed-loop (live) calibration mode allows the measurement device to continuously read the display while adjustments are made in real time, providing instant feedback without manual switching.
Question 7: An ISF calibrator tests a display and finds that its color gamut covers 95% of DCI-P3 but the content is mastered in Rec. 709. Without proper gamut mapping, how will colors appear?
- Undersaturated and dull
- Oversaturated and vivid beyond reference (Correct answer)
- Correct, because the display covers a larger gamut
- Desaturated in reds only
Correct answer: Oversaturated and vivid beyond reference
Without gamut mapping or a correct color space setting, a wide-gamut display will overdrive Rec. 709 signals, producing colors that are more saturated than the creator intended.
ISF Testing Equipment & Troubleshooting Methods 5
A client reports that skin tones look orange on their calibrated display but the grayscale and color checker measurements passed.
What should the calibrator investigate first?