Pro Colorist Answers Questions on SDR Peak Luminance, Aspect Ratio Management, Look Development, and Contrast Shaping in DaVinci Resolve

Cullen Kelly

Peak Luminance for SDR Displays [2:28]

• There is no official standard requiring SDR displays to be graded at exactly 100 nits.
  • The speaker personally drives his displays at 120 nits in a controlled environment.
  • For less controlled lighting conditions, a higher peak luminance like 150-160 nits might be preferred.
• Calibrating a MacBook Pro for SDR grading:
  • A professional calibrator set the speaker's MacBook Pro to 120 nits with the brightness slider at approximately 35%.
  • A rough estimate for users without professional calibration is to set the brightness slider to around 33% for comfortable viewing.
  • The goal is comfort and a consistent working environment rather than hitting an exact, arbitrary number.

Dealing with Different Aspect Ratios [6:50]

• The concept of a "geometry pipeline" is introduced, mirroring a color pipeline (input, working, output).
  • It consists of three stages for managing image geometry:
    1. Captured Resolution and Aspect Ratio: The native format of the source footage.
    2. Canvas (Timeline) Resolution and Aspect Ratio: The desired intermediate workspace for grading.
    3. Output Display Resolution and Aspect Ratio: The final display format.
• Practical Example with DaVinci Resolve:
  • Source footage: 2880x2160 with a 2x pixel aspect ratio, resulting in an effective 5760x2160 [2.66:1] image.
  • Desired canvas: 4K DCI scope at 4096x1716 [2.39:1].
  • Output display: 3840x2160 (16:9).

    

• Key Principles for Geometry Pipeline Settings in Resolve:
  • Input Scaling (Camera to Canvas): Set to "scale full frame with crop."
    • This ensures the entire frame fills the canvas, cropping any excess width/height without introducing black bars (padding) at this stage.
    • Rationale: Avoids grading unintentional black bars as part of the active image area, which can lead to color shifts in those areas.
  • Output Scaling (Canvas to Display): Set to "scale entire image to fit."
    • This allows the canvas (your intended image) to fit entirely onto the monitoring display, introducing letterboxing or pillarboxing as needed at the display stage.
    • Rationale: The padding is generated by the display mapping, not as part of the graded image, preserving the artistic intent of the canvas.
  • Defining the Canvas: The most crucial decision, determining the project's ideal resolution and aspect ratio (e.g., 4K DCI 2.39:1).
  • Defining Output Resolution: Should precisely match the monitoring display's native resolution.

    

Is Your Grade Overdone? [26:52]

• "If you don't go, you won't know": The best way to understand when a grade is "too much" is to intentionally push it beyond what looks good.
  • This process helps identify the boundaries and characteristics of an adjustment.
• Finding the Right Balance:
  • Once you've pushed an adjustment too far and clearly recognize it as such, you have a "goalpost."
  • You can then dial back the adjustment either manually (e.g., unwinding a trackball) or by using the "Key Output Gain" control on the node.
    • Key Output Gain acts as an opacity control for the entire node, allowing you to reduce the overall intensity of all adjustments within that node with a single slider.
    • This is particularly useful when an adjustment feels "really good, but just too much of it."

JPLog2 Working Space [33:00]

• The speaker has analyzed the JPLog2 specification but remains skeptical about its claimed unique advantages.
  • Questionable Benefits: Many touted benefits, such as even spacing between stops, are inherent to all logarithmic encodings, not exclusive to JPLog2.
  • Dynamic Range Allocation Concerns: The way JPLog2 allocates dynamic range (e.g., for extra headroom) can make standard grading tools (like lift, gamma, gain) feel "weird" or unintuitive.
    • The distribution of highlights and the higher gray point compared to other log curves (like ARRI LogC4) may complicate traditional grading workflows.
• Grading in Linear Space for Exposure:
  • Regardless of the chosen log working space, adjusting exposure (gain) is often best performed in a linear color space for predictable, photometric results.
  • Applying linear gain (multiplying by powers of two for f-stops) ensures accurate exposure changes.
  • Other adjustments, like lift, gamma, and gain, will behave differently depending on the specific log curve, influencing the "feel" of the tools.

Lifting Shadows Photometrically [38:57]

• Photometric vs. Aesthetic Adjustments:
  • "Photometric" refers to adjustments that simulate real-world light changes, like f-stops.
  • While precise photometric shadow lifting is complex, linear gain adjustments in a linear color space are the closest equivalent to photometric exposure changes.
    • Moving gain in powers of two corresponds to changing f-stops.
  • Contrast/Pivot for Linear Contrast:
    • Using the contrast/pivot control in DaVinci Resolve with the pivot set to the middle gray of your system (e.g., 0.336 for DaVinci Intermediate) achieves a linear contrast adjustment without shifting the middle gray. This is considered a foundational principle for photometric contrast.

      

• Shift from Scene-Referred to Display-Referred Thinking:
  • There's a natural transition in color grading where the focus moves from scene-referred (photometric accuracy) to display-referred (aesthetic rendering).
  • At a certain point, adjustments are made based on how the image looks and feels on screen, rather than strict adherence to real-world light ratios.
  • This shift is a motivator behind certain node graph constructions, where a "prime" node might handle initial exposure and then allow for more artistic shaping with lift, gamma, and gain, prioritizing visual appeal.

Improving Look Development [48:09]

• Embrace the "Itch" for Control:
  • Feeling unsatisfied with existing LUTs (like Kodak print LUTs) and desiring more control is a common and positive driver for skill development in look creation.
• Leverage Existing Looks as Learning Tools:
  • It's important to understand that using a well-made, off-the-shelf LUT doesn't diminish a colorist's skill.
  • Instead of abandoning preferred LUTs, use them as a high benchmark.
  • Continuously practice building your own looks, aiming to surpass or match the quality of your favorite commercial LUTs. Keep using the commercial LUTs for client work until your custom looks are superior.
• Structured Learning and Tools:
  • Tools like "Contour" (the speaker's plugin) are designed to provide a structured approach to look development, breaking down the process into manageable modules.
  • Such tools often come with educational resources (e.g., deep-dive courses, manuals explaining each option) that can accelerate the learning process.

    

• Learn Informally and Discern:
  • Explore various online resources for look development, but be prepared to critically evaluate the advice given.
  • The journey often involves trying different techniques, observing results, and refining your approach based on what consistently yields good outcomes.

Shaping Contrast and Color Balance [54:55]

• Contrast as the Core of Color Grading:
  • Contrast is not merely a "small, medium, or large" axis but rather the smooth remapping of output values for every input value.
  • It manifests in various forms:
    • Tonal Contrast: Differences in brightness and darkness.
    • Color Contrast: Differences in hue and saturation.
    • Spatial Contrast: Differences in detail and texture across the image.
• The Importance of a Strong Look Foundation:
  • Achieving "clean, clear, distinct" and "popping" images is best accomplished not just through grading-level color balance and contrast adjustments, but primarily through a robust "imaging pipeline" established during look development.
  • A well-designed look (LUT or DCTL) provides a strong foundation, meaning the footage already looks good before shot-by-shot grading begins.

    

• Shifting Grading Mindset from "Fixing" to "Enhancing":
  • When the foundational look is strong, the colorist can approach individual shots with a creative mindset, exploring artistic possibilities rather than solely focusing on technical corrections.
  • This allows for a more enjoyable and efficient grading process, where the goal is to elevate an already pleasing image.
  • It is possible, even with challenging footage, to establish a look that makes the image appealing from the outset, enabling more creative choices during grading.