8.3 HDR color grading and mastering

HDR color grading and mastering elevate cinematography by capturing a wider range of luminance and color. This technique allows for more realistic visuals, preserving details in both bright highlights and dark shadows. The process involves specialized workflows and tools to maximize HDR's expanded capabilities.

Mastering HDR content requires advanced color grading techniques, ACES color management, and HDR reference monitors. Filmmakers must consider creative uses of expanded contrast ratios and vivid color palettes. Challenges include lack of standards, inconsistent viewing experiences, and increased storage and bandwidth requirements.

HDR vs SDR

• High Dynamic Range (HDR) is a technique used in cinematography to capture and display a wider range of luminance and color compared to Standard Dynamic Range (SDR)
• HDR allows for more realistic and immersive visuals by preserving details in both the brightest highlights and darkest shadows of a scene

increased dynamic range

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Top images from around the web for increased dynamic range

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• HDR captures a broader range of luminance values, typically measured in stops or the ratio between the brightest and darkest parts of an image
  • SDR typically has a dynamic range of around 6-10 stops
  • HDR can capture and display up to 20 stops or more
• Increased dynamic range allows for more detail and contrast in both highlights and shadows
  • Bright areas like sky or reflections maintain detail and texture instead of clipping to pure white
  • Dark areas reveal more shadow detail and subtle gradations instead of crushing to black

wider color gamut

• HDR utilizes a wider color gamut, meaning it can reproduce a larger range of colors compared to SDR
  • SDR uses the Rec. 709 color space, which covers about 35% of the visible color spectrum
  • HDR commonly uses the Rec. 2020 color space, covering about 75% of the visible spectrum
• Wider color gamut allows for more vivid, saturated, and lifelike colors
  • Deeper reds, greens, and blues that were previously outside the range of SDR displays
  • More accurate representation of real-world colors and subtle hue variations

HDR standards and formats

• Several HDR standards and formats have emerged, each with different specifications and capabilities
  • HDR10 is an open standard that uses 10-bit color depth and static metadata (Samsung, Sony, LG)
  • Dolby Vision is a proprietary format that uses 12-bit color and dynamic metadata (LG, Vizio, TCL)
  • HDR10+ is an enhanced version of HDR10 that adds dynamic metadata (Samsung, Panasonic, 20th Century Fox)
  • Hybrid Log-Gamma (HLG) is a broadcast-focused HDR format developed by the BBC and NHK
• Lack of a unified standard has led to some confusion and compatibility issues for consumers and content creators

Mastering HDR content

• Mastering HDR content involves a specialized workflow and tools to ensure the final video takes full advantage of the expanded capabilities of HDR displays
• Proper HDR mastering is crucial for delivering a consistent, high-quality viewing experience across different devices and platforms

color grading workflow

• HDR color grading typically starts with a log or raw video source that preserves the full dynamic range of the original camera capture
• Colorists use advanced grading tools and HDR reference monitors to make creative adjustments and optimize the image for HDR delivery
  • Adjusting lift, gamma, and gain to set the overall contrast and tonal balance
  • Fine-tuning colors, saturation, and hue to take advantage of the wider color gamut
  • Applying HDR-specific tools like highlight recovery, shadow detail enhancement, and color space conversion

ACES color management

• The Academy Color Encoding System (ACES) is a device-independent color management framework designed to simplify HDR workflows
• ACES provides a common color space and a set of best practices for managing color throughout the production pipeline
  • Converts input footage from various cameras and sources into the ACES color space
  • Allows for consistent color grading and visual effects work regardless of the original format
  • Outputs the final grade to multiple delivery formats (HDR10, Dolby Vision, SDR) with minimal additional work

HDR reference monitor

• An HDR reference monitor is essential for accurately evaluating and grading HDR content
• These specialized displays offer:
  • High peak brightness (1000+ nits) to properly display HDR highlights
  • Wide color gamut (Rec. 2020 or P3) to show the full range of HDR colors
  • Precise calibration and color accuracy for consistent results
  • Examples include the Sony BVM-HX310, Canon DP-V2421, and Flanders Scientific XM311K

HDR metadata

• HDR metadata is additional information embedded in the video signal that tells the display how to interpret and map the HDR image data
• Static metadata (HDR10) includes:
  • Maximum and minimum luminance levels for the entire video
  • Color primaries and white point
  • Electro-optical transfer function (EOTF)
• Dynamic metadata (Dolby Vision, HDR10+) changes on a scene-by-scene or frame-by-frame basis
  • Allows for more precise and adaptive tone mapping based on the content
  • Can optimize contrast and color for each scene, resulting in a more impactful HDR experience

HDR deliverables

• Mastering HDR content often involves creating multiple deliverables to accommodate different distribution platforms and display capabilities
  • HDR10 or HDR10+ for streaming services like Amazon Prime Video, Netflix, and Ultra HD Blu-ray
  • Dolby Vision for compatible TVs and streaming platforms
  • HLG for live broadcast and cable/satellite TV
  • SDR version derived from the HDR grade for older displays and backwards compatibility
• Each deliverable may require specific encoding settings, metadata, and quality control checks to ensure optimal performance on the intended platform

Creative use of HDR

• HDR opens up new creative possibilities for cinematographers and colorists to enhance the visual storytelling and emotional impact of their projects
• By understanding the unique characteristics and capabilities of HDR, filmmakers can make informed decisions throughout the production process to maximize its potential

expanded contrast ratio

• The increased contrast ratio of HDR allows for more dramatic and realistic lighting setups
  • Preserve bright highlights like practical lights, sun flares, or explosions without clipping
  • Maintain rich shadow detail in low-light scenes or nighttime environments
  • Create a greater sense of depth and dimensionality through the interplay of light and shadow
• Cinematographers can use the expanded contrast to guide the viewer's attention, evoke specific moods, or emphasize narrative elements

vivid color palette

• The wider color gamut of HDR enables a more expressive and vibrant visual style
  • Saturated and bold colors can be used to create striking visual designs or convey heightened emotions
  • Subtle hue variations and delicate pastels can add realism and nuance to natural landscapes or intimate scenes
  • Creative use of color can establish visual themes, symbolism, or character associations
• Colorists have more precision and control over the final look, allowing them to fine-tune the palette to support the story and artistic intent

HDR vs SDR aesthetic

• HDR can produce a different aesthetic compared to traditional SDR content
  • Images may appear more lifelike, immersive, and "window-like" due to the increased contrast and color fidelity
  • Some viewers may find HDR content to look hyper-real or overly stylized, especially when pushed to extremes
• Filmmakers should consider the creative intent and target audience when deciding how to use HDR
  • A more naturalistic and subtle approach may be appropriate for dramas or documentaries
  • A bolder and more heightened look may suit action films, sci-fi, or fantasy genres
  • Consistency and restraint are important to avoid visual fatigue or distraction from the story

lighting for HDR

• HDR requires a more thoughtful and controlled approach to lighting on set
• Cinematographers need to be mindful of the increased dynamic range and how it affects the balance between highlights and shadows
  • Careful placement and shaping of light sources to avoid excessive contrast or clipping
  • Use of diffusion, bounce, or negative fill to control the light ratios and maintain detail in both ends of the luminance range
  • Collaboration with the production designer to select appropriate practical fixtures and materials that work within the HDR palette
• On-set monitoring in HDR is crucial for making informed lighting decisions and avoiding surprises in post-production

HDR scene referred workflow

• A scene referred workflow involves capturing and grading the image based on the actual light values present in the scene, rather than a display-referred output
• This approach preserves the full dynamic range and color gamut of the original scene, allowing for greater flexibility and control in post-production
  • Capture log or raw video that retains the maximum amount of image data
  • Use on-set tools like waveform monitors and HDR reference displays to ensure proper exposure and lighting
  • Grade the footage in a wide color space (ACES or camera-native) to maintain the scene referred values
  • Apply a display-referred output transform (HDR10, Dolby Vision) for the final deliverable
• A scene referred workflow is especially beneficial for HDR, as it allows the colorist to make the most of the expanded luminance and color range without compromising the original creative intent

HDR display technologies

• The development of HDR display technologies has been crucial in enabling the widespread adoption of HDR content in consumer homes
• Several different types of HDR displays are available, each with its own strengths, limitations, and price points

OLED vs LED

• OLED (Organic Light Emitting Diode) and LED (Light Emitting Diode) are two common technologies used in HDR displays
• OLED displays:
  • Each pixel emits its own light, allowing for perfect black levels and infinite contrast
  • Wider viewing angles and more uniform brightness across the screen
  • Thinner and more flexible panel designs
  • More expensive to manufacture, limited peak brightness compared to LED
• LED displays:
  • Use an LED backlight system to illuminate an LCD panel
  • Higher peak brightness levels (1500+ nits) suitable for HDR
  • More affordable and available in larger sizes
  • Reduced contrast and black levels compared to OLED, potential for backlight blooming artifacts

dual layer LCDs

• Dual layer LCD is an emerging technology that combines two LCD panels stacked on top of each other
• The rear panel is a monochrome LCD that modulates the backlight, while the front panel is a traditional color LCD
• Benefits of dual layer LCD for HDR:
  • Increased contrast ratio and deeper black levels compared to single layer LCD
  • Higher peak brightness and wider color gamut than OLED
  • Reduced halo effect and improved local dimming performance
• Examples include the Hisense U9E and the Panasonic MegaCon prototype

tone mapping for SDR

• Tone mapping is the process of converting HDR content to be displayed on SDR screens with limited dynamic range
• HDR displays use tone mapping to ensure compatibility with existing SDR content and sources
  • Static tone mapping applies a fixed curve to compress the HDR luminance range into the SDR space
  • Dynamic tone mapping analyzes the content and adapts the curve on a scene-by-scene or frame-by-frame basis
• Effective tone mapping preserves the overall contrast, color, and creative intent of the HDR grade while avoiding clipping or excessive darkening of the image

HDR calibration

• Proper calibration is essential for ensuring that HDR displays accurately reproduce the intended image
• Key aspects of HDR calibration include:
  • Setting the peak luminance and black level to match the content and viewing environment
  • Adjusting the color space and white point to the appropriate standard (Rec. 2020, DCI-P3)
  • Measuring and correcting for any color or luminance inaccuracies across the screen
  • Verifying the display's performance with HDR test patterns and content
• Professional calibration tools like colorimeters, spectroradiometers, and HDR signal generators are used to achieve the most accurate results

consumer HDR displays

• A wide range of consumer HDR displays are now available, offering varying levels of performance and features
• Key factors to consider when evaluating consumer HDR displays include:
  • Peak brightness and contrast ratio
  • Color gamut coverage (Rec. 2020, DCI-P3)
  • Local dimming capabilities and number of zones
  • Supported HDR formats (HDR10, Dolby Vision, HDR10+, HLG)
  • Viewing angle and screen uniformity
  • Input lag and gaming features for interactive content
• Notable examples include the LG C1 OLED, Samsung QN90A QLED, and Sony X95J LED

Challenges of HDR adoption

• Despite the benefits and advancements in HDR technology, several challenges remain that hinder its widespread adoption in the content creation and consumer markets
• Addressing these challenges will be crucial for realizing the full potential of HDR and ensuring a consistent, high-quality experience for viewers

lack of standards

• The existence of multiple competing HDR formats and standards has led to confusion and fragmentation in the market
  • Different formats (HDR10, Dolby Vision, HDR10+, HLG) with varying specifications and capabilities
  • Inconsistent support across devices, content platforms, and distribution channels
  • Confusion for consumers when purchasing HDR devices or content
• Efforts to establish a unified, open standard for HDR have been met with resistance from companies invested in proprietary formats
• Greater collaboration and interoperability between industry players would simplify the HDR landscape and accelerate adoption

inconsistent viewing experiences

• The wide range of HDR display capabilities and settings can result in inconsistent viewing experiences for consumers
  • Variations in peak brightness, color gamut, and tone mapping algorithms between devices
  • Incorrect or suboptimal display settings that do not match the content or viewing environment
  • Differences in HDR performance between display technologies (OLED, LED, dual layer LCD)
• These inconsistencies can undermine the impact and intent of HDR content, leading to viewer dissatisfaction or disinterest
• Improved consumer education, standardized settings, and more robust metadata could help ensure a more consistent HDR experience across devices

increased storage and bandwidth

• HDR content requires significantly more storage space and bandwidth compared to traditional SDR video
  • Higher bit depth (10-bit or 12-bit) and color sampling (4:2:2 or 4:4:4) for increased color precision
  • Larger file sizes due to the additional data needed to represent the expanded luminance and color range
  • Higher bitrates for streaming or broadcasting HDR content to maintain quality and avoid compression artifacts
• These increased requirements can strain existing storage and network infrastructures, particularly for 4K or 8K resolution HDR content
• Advances in compression techniques (HEVC, AV1), more efficient file formats, and improved broadband speeds will be necessary to support the growth of HDR content delivery

backwards compatibility with SDR

• Ensuring backwards compatibility with existing SDR displays and content is a significant challenge for HDR adoption
• HDR content needs to be properly tone mapped or down-converted to SDR for viewing on non-HDR displays
  • Maintaining the creative intent and visual quality of the HDR grade in the SDR version
  • Avoiding artifacts, clipping, or excessive darkening during the tone mapping process
  • Providing separate SDR deliverables or metadata for optimal compatibility
• Legacy SDR content may also require upscaling or enhancement to take advantage of HDR display capabilities, which can introduce additional artifacts or inconsistencies
• Careful planning and testing throughout the production and distribution pipeline are necessary to ensure a seamless experience for both HDR and SDR viewers

cost of implementation

• Implementing HDR in content production and distribution workflows involves significant costs and resources
  • Upgrading cameras, monitors, and post-production equipment to support HDR
  • Additional time and skilled personnel for HDR grading, quality control, and mastering
  • Increased storage and bandwidth costs for managing and delivering HDR content
  • Need for multiple versions or deliverables to accommodate different HDR formats and SDR compatibility
• On the consumer side, HDR-capable displays and devices often come at a premium price compared to their SDR counterparts
• These costs can be a barrier to entry for smaller content creators, distributors, and consumers, slowing the overall adoption of HDR
• As technology advances and economies of scale improve, the cost of implementing HDR is expected to decrease over time, making it more accessible to a wider range of stakeholders