Video Editing Color and Image Treatment Flashcards

24 sample cards from the Color and Image Treatment deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. What is day-for-night grading and what adjustments create the illusion?

   Day-for-night is grading footage shot in daylight to look like night. Typical moves: strongly lower overall exposure (especially highlights), crush shadows, desaturate, shift the balance toward blue (moonlight convention), and darken or replace the sky, since our night vision perceives little color.

2. What is a LUT in color grading?

   A LUT (Look-Up Table) is a precomputed table that maps input color values to output color values — effectively a saved color transform. LUTs are used to convert between color spaces (technical LUTs) or to apply a stylistic look (creative LUTs), and are portable across software and hardware.

3. What is the difference between a 1D LUT and a 3D LUT?

   A 1D LUT maps each channel independently ($R \to R$, $G \to G$, $B \to B$), so it can only alter tone/contrast per channel — it cannot change hue or saturation relationships. A 3D LUT maps every RGB combination into a 3D lattice (e.g., a $33 \times 33 \times 33$ cube $= 35{,}937$ nodes, interpolated between), allowing complex hue, saturation, and crosstalk transforms.

4. Distinguish a technical (conversion) LUT from a creative LUT.

   A technical LUT performs a mathematically defined color space/gamma conversion — e.g., S-Log3 to Rec. 709 — to normalize footage; it is not a matter of taste. A creative LUT applies an artistic look (film stock emulation, teal-orange, etc.) on top of already-normalized footage. Correct order: technical conversion first, creative look after.

5. Why do cameras record in logarithmic (log) gamma profiles such as S-Log3 or C-Log?

   Log encoding redistributes the camera sensor's wide dynamic range into the limited code values of the file, allocating more values to shadows and mid-tones. The footage looks flat, low-contrast, and desaturated straight from camera, but preserves maximum highlight/shadow detail for grading; it must be normalized (via LUT or color management) before delivery.

6. Why should exposure and white balance corrections be applied before a Rec. 709 conversion LUT rather than after it?

   A conversion LUT clips any values outside its expected input range — data pushed past its boundaries is permanently discarded downstream of the LUT. Correcting exposure/balance before (upstream of) the LUT works on the full log data, so highlight and shadow detail can still be recovered; correcting after the LUT manipulates already-clipped output.

7. In node-based grading (e.g., DaVinci Resolve), what is a serial node and how does it process the image?

   A serial node is connected in a chain, receiving the output of the previous node as its input. Corrections therefore compound in order: each node grades the image as already modified by all upstream nodes — which is why fixing exposure in node 1 changes how a qualifier in node 2 behaves.

8. What is a parallel node structure and when is it preferred over serial nodes?

   Parallel nodes all receive the same input image, and their corrections are combined (mixed) into one output. It is preferred when making several independent secondary corrections (e.g., separate keys for skin, sky, and foliage) that should each key off the same source image without one selection being altered by another's correction.

9. Why does node/operation order matter in a grade? Give a classic example.

   Because each operation feeds the next, the same corrections in a different order give different results. Classic example: an HSL qualifier keys much more cleanly after the image has been balanced and normalized (contrast/saturation restored from log) than on flat log footage — so balance in an early node, qualify in a later one.

10. What is an adjustment layer in layer-based grading applications like Premiere Pro?

    An adjustment layer is an empty layer placed on a track above clips; any effect or grade applied to it affects every clip below it for its duration. It is used to apply one shared grade, look, or LUT across many shots at once, with lower layers processed first and stacked effects compositing top-down.

11. Compare the peak luminance and dynamic range of SDR and HDR video.

    SDR is mastered for a peak of about $100\ \mathrm{cd/m^2}$ (nits) with roughly $6$ stops of display dynamic range, using a gamma curve. HDR supports peaks from $1000$ up to $10{,}000\ \mathrm{cd/m^2}$ (PQ ceiling) with much deeper blacks, wider dynamic range, and typically wide color gamut plus at least 10-bit depth.

12. What is the PQ transfer function used in HDR?

    PQ (Perceptual Quantizer, standardized as SMPTE ST 2084) is an absolute HDR transfer function that maps code values to exact luminance levels from $0$ to $10{,}000\ \mathrm{cd/m^2}$, with steps sized to human contrast perception. It underlies HDR10 and Dolby Vision; being absolute, it is not backward compatible with SDR displays.

13. What is HLG and what is its key advantage for broadcasters?

    HLG (Hybrid Log-Gamma), developed by the BBC and NHK, is a relative, scene-referred HDR transfer function: a conventional gamma curve in the lower range with a logarithmic curve for highlights. Its key advantage is backward compatibility — one HLG signal displays acceptably on both SDR and HDR screens without metadata, ideal for live broadcast.

14. Compare HDR10 and Dolby Vision.

    HDR10: open standard, 10-bit, PQ curve, static metadata (one set of brightness values for the whole program). Dolby Vision: proprietary/licensed, up to 12-bit, PQ curve, dynamic metadata that adjusts tone mapping scene-by-scene or frame-by-frame, generally giving more accurate rendering on displays of varying capability.

15. What is Rec. 709 and what are its key parameters?

    Rec. 709 (ITU-R BT.709) is the standard color space for HD SDR television and most web video. Key parameters: relatively small color gamut, D65 white point, display gamma of approximately $2.4$ (commonly handled as $\approx 2.2$–$2.4$), $100\ \mathrm{cd/m^2}$ reference white, legal range luma of $16$–$235$ in 8-bit.

16. What is Rec. 2020 and how does it differ from Rec. 709?

    Rec. 2020 (ITU-R BT.2020) is the color standard for UHD/4K/8K television, defining a much wider color gamut (covering roughly $75.8\%$ of the CIE 1931 visible spectrum versus about $35.9\%$ for Rec. 709), D65 white point, and 10- or 12-bit depth. It is mainly used as a container gamut for HDR delivery, since no consumer display fully covers it.

17. What is DCI-P3 and where is it used?

    DCI-P3 is the color gamut standard for digital cinema projection, defined by the Digital Cinema Initiatives. It is about $25\%$ larger than Rec. 709 (covering roughly $53.6\%$ of visible colors), with notably richer reds and greens. Variants (Display P3, D65) are widely adopted in phones, tablets, and HDR consumer displays.

18. Rank the gamuts Rec. 709, DCI-P3, and Rec. 2020 by size and state their containment relationship.

    From smallest to largest: $\text{Rec. 709} \subset \text{DCI-P3} \subset \text{Rec. 2020}$. Rec. 709 is the smallest (HD SDR), DCI-P3 is intermediate (cinema and most real HDR displays), and Rec. 2020 is the largest (UHD/HDR container gamut).

19. What are legal (video/limited) range levels versus full (data) range levels in 8-bit and 10-bit video?

    Legal/video range reserves headroom and footroom: in 8-bit, black $= 16$ and white $= 235$ (chroma $16$–$240$); in 10-bit, black $= 64$ and white $= 940$. Full/data range uses the entire scale: $0$–$255$ (8-bit) or $0$–$1023$ (10-bit). Broadcast delivery requires legal range; a range mismatch makes footage look washed out or crushed.

20. What are broadcast-safe signal limits, and what are superwhites and superblacks?

    Broadcast specs require the luma signal to stay between $0$ and $100\ \mathrm{IRE}$ (black to reference white), with chroma/RGB excursions also within legal bounds. Superwhites are values above $100\ \mathrm{IRE}$ (above code 235/940) and superblacks are values below $0\ \mathrm{IRE}$; both are illegal for broadcast and will be clipped or cause QC rejection, transmission artifacts, or distortion.

21. How does a colorist ensure a program is broadcast safe before delivery?

    By monitoring waveform/parade scopes against $0$–$100\ \mathrm{IRE}$ limits during the grade, keeping saturation within legal gamut, and applying a broadcast-safe limiter/clip as the final operation in the chain (e.g., a final node or output effect) to catch stray excursions. Delivery files are then verified against the broadcaster's QC spec.

22. What is the difference between a display-referred and a scene-referred (color-managed) grading workflow?

    Display-referred: footage is transformed (often by eye or LUT) directly for one target display standard (e.g., Rec. 709); the grade is baked toward that display. Scene-referred/color-managed: images are converted into a common wide working space representing scene light, graded there, and then rendered to any output through display transforms — making grades portable across SDR, HDR, and cinema deliverables.

23. What is ACES, and what do the IDT, RRT, and ODT stages do?

    ACES (Academy Color Encoding System) is an open, standardized scene-referred color management pipeline for mixing cameras and delivering to multiple formats. IDT (Input Device Transform) converts each camera's native encoding into the ACES working space; RRT (Reference Rendering Transform) applies the standard filmic rendering; ODT (Output Device Transform) maps the result to a specific display standard (Rec. 709, P3, Rec. 2100, etc.).

24. What are the reference settings for a calibrated SDR grading monitor, and why is calibration essential?

    SDR reference: D65 white point ($\approx 6500\,\mathrm{K}$), gamma $2.4$, peak white at $100\ \mathrm{cd/m^2}$, evaluated in a dim, neutral environment; calibration is performed with a measurement probe (colorimeter/spectroradiometer). Without a calibrated display the colorist compensates for the monitor's errors, baking opposite errors into the grade for every other screen.

What this deck covers

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