This article intends to help productions successfully navigate on-set HDR workflows. While we encourage the viewing of HDR images early in the production process, it is not a Netflix requirement to have HDR monitoring on-set.
Netflix is available to assist in navigating production-specific workflow decisions in collaboration with key production stakeholders. Please reach out to your Netflix contacts with any questions or concerns specific to your production.
Table of Contents
- Choosing a Monitor
- Viewing Environment Considerations
- Display Performance
- Color Management
- Signal Distribution & On-Set Equipment Recommendations
Choosing a Monitor
Panel and Backlight Types:
Traditional LCDs can struggle to provide the deep blacks and wide viewing angles required for optimal HDR monitoring. Local-dimming can improve LCD dynamic range, but cheaper implementations suffer from issues like "blooming" and "halo" effects.
Global dimming LCDs, which dynamically adjust the entire backlight, are unreliable for static image monitoring, a common part of on-set workflows. Dual-layer LCDs offer a more stable alternative by separating luminance and color tasks, but these types of monitors are very heavy, expensive and not generally used for on set monitoring.
OLED displays, with each pixel's ability to independently emit light, provide the best HDR performance with perfect blacks and wide viewing angles, making them well-suited for on-set use. However, OLED technology is generally more expensive than LCD.
Newer technologies like Quantum-Dot or QD-OLED and RGB OLED offer potential advantages over traditional OLED (White OLED or WOLED), such as wider color gamut, higher peak luminance, wider viewing angle and improved efficiency.
Note: Beware of "BSDR" or "Bright SDR" monitors, which are often marketed as "HDR-capable" despite having limited dynamic range compared to true HDR displays. These compromised products can be unsuitable for critical on-set HDR monitoring.
Viewing Environment Considerations
There are pros and cons to each display technology, depending on how they will be used in a given production. LCDs can typically achieve higher peak brightness due to the backlight nature, which may be important in a sunny outdoor setting or brighter overall viewing conditions. In a more controlled, darker viewing environment, the enhanced black level performance of QD OLED and RGB OLED pixels can add significantly to the overall dynamic range on a static image and offer a wider viewing angle.
Viewing Angle
Viewing angle is an important consideration for any display, especially on-set, where there are often multiple viewers of the same monitor standing at different angles. Factors that affect viewing angle include the display type (see “Panel and Backlight Types” in the Appendix), the reflectivity of the screen (matte vs. glass), the viewing environment, and monitor position. In a perfect world, the display luminance and color should be the same when viewed from any angle--horizontal or vertical.
Size & Form Factor
The physical dimensions, weight, ergonomics, durability, and noise of displays are all factors that should be taken into consideration when designing an HDR viewing environment. New panel technologies like QD-OLED are accelerating the availability of light weight, durable HDR monitor solutions more optimized for on-set use.
Image courtesy of Panavision
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Power Consumption & Fan Noise
- HDR monitors can consume a lot of power and may require fans, which can be problematic depending on monitor proximity to the set.
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Weight
- Currently, the technologies that drive a high-quality HDR monitor can add weight to the monitor itself depending on the display technology used. Smaller and lighter units, while easier to transport and set up, may be fragile and challenging to repair on location.
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Operational Temperature Range
- When working in more “extreme” conditions, it’s best to follow the manufacturer’s guidance for optimal temperature ranges.
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Rack and VESA Mountability
- Because of their weight, some HDR monitors may require more robust mounting solutions than others, which can impact considerations around equipment transport and selecting viable locations for the viewing environment on-set.
Display Performance
Peak Luminance
The minimum peak luminance of a reference monitor used for color grading in Dolby Vision HDR is 1000 nits (a ‘nit’ is a term used to describe luminance or brightness of a display). Ideally, an HDR on-set monitor should have the same peak luminance as the final reference monitor, but this is not always possible with today’s available technology. When considering an HDR monitor for on-set use, a higher priority than peak nit level is a display’s ability to simultaneously (and sustainably) produce bright white levels and sufficiently dark black levels so as to reveal accurate image data in the highlights and shadows.
Contrast Ratio
Contrast ratio is the ratio from the peak brightness to the minimum black level of a display, usually measured in the ratio - light:dark. For example, a 1000 nit display with a black level of 1 nit, would have a 1000:1 contrast ratio. That said, when it comes to consumer displays, marketing has effectively rendered this metric meaningless, with scientifically inaccurate terms like “infinite contrast ratio” commonly used.
As such, there is no reliably marketed benchmark available to best compare the quality of these displays in terms of contrast ratio. Hands-on evaluations can help key stakeholders understand the nuance of each available option. With both SDR and HDR displays, it is critically important to test and calibrate your monitors.
Color Gamut
Most HDR monitors support using either P3-D65 or BT.2020 color gamuts, which are capable of showing more highly-saturated colors in the scene than the traditional Rec. 709 gamut of SDR monitors. This combination of a wider luminance range and color gamut is often referred to as a larger “color volume” - capable of displaying more of the colors and light levels that exist in the real world. HDR monitors vary in their exact color gamuts, but most have the ability to cover 95+% of P3 and 80-90% of Rec.2020.
Color Management
Having a solid color management plan is crucial for a number of reasons, but it is especially important when planning to monitor HDR on-set. This starts by using the same color management framework for both SDR and HDR signal paths, rather than different color management frameworks for each. This way, the production will be comparing SDR and HDR through the same color management framework, rather than comparing SDR and HDR with different frameworks. For example, when using ACES color management, it should be used for both SDR and HDR paths, rather than the camera manufacturer’s SDR (in-camera) and ACES for HDR (external).
See “What Is Color Management” for a more in-depth explanation of this topic.
Signal Distribution & On-Set Equipment Recommendations
Camera Output
- Color space: Log recommended.
- Bit depth: 10-bit minimum.
- Color subsampling: 4:4:4 or 4:2:2 minimum .
- Resolution: 4K resolution is ideal, but HD (1920x1080) resolution is sufficient.
Signal Distribution
Cabled distribution:
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SDI signal:
- Minimum 10-bit 4:2:2 required for HDR monitoring.
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Signal Splitting / Distribution:
- At a minimum, have a properly rated 3G-HD-VDA (Video Distribution Amplifier) to distribute signals to multiple downstream monitors.
- A router / switcher, properly rated for the type of signal anticipated, e.g. 3G-SDI vs 12G-SDI vs HDMI can be used. Included in this would be a Router Panel for each monitor for which a signal would be distributed. This enables the operator to select what specific signal to monitor.
Wireless distribution:
- The minimum specification for wirelessly transmitting an HDR signal requires systems that work in 10-bits or higher and are capable of transmitting the color space of 4:2:2.
- If you are in a multi-cam / live-to-tape situation, you may elect to use systems that enable additional enhancements for control and/or telemetry for control data.
Light Meters
While a light meter remains an important and effective tool to inform exposure and lighting decisions, measured lighting ratios may need to be adjusted for HDR to account for the differences in roll-off, shadows, and background details. For example, if a key light on one side of the talent’s face appears brighter in HDR than in SDR, the key light or fill light may be adjusted to achieve an appropriate balance. Implementing HDR monitoring on-set, in conjunction with the use of a light meter and other tools, can help to inform these types of lighting ratio decisions.
Scopes
Scopes are often used to evaluate image signal and exposure to avoid potential clipping during on-set monitoring; however, SDR and HDR use different curves, or EOTF’s (Electro-optical Transfer Functions), for those calculations. This means that operators will have to re-train themselves on how to interpret scope outputs when working in HDR or upgrade their scopes to models that can represent an HDR signal appropriately.
Gamma (Rec. 709)
SDR signals use a 2.4 “gamma” EOTF standardized as BT.1886. This places a peak white of 100 nits at a signal level of 100%, black (0 nits) at a signal level of 0%, and the remaining range is modified using a 2.4 power function. This means that typical imagery will fall in the ‘middle’ of the scopes because the highlights and shadows were compressed in the top and bottom.
PQ (ST. 2084)
With the advent of HDR, a new EOTF was defined called PQ, which stands for Perceptual Quantizer. PQ is standardized as SMPTE ST.2084. Instead of encoding 100 nits into a simple power function, the PQ curve encodes 0 to 10,000 nits and uses a curve modeled after the human visual system’s response to luminance differences. This is done to optimize the use of every code value (CV) across the whole luminance range. This means that typical imagery will generally fall on the lower portion of the scope.
Live Grading Software and LUTs
For HDR monitoring, it is important to ensure the hardware involved in the HDR monitoring pipelines on-set (such as monitors, LUT boxes, etc) supports a minimum of 33x sized 3D LUTs which provide more precise conversion and fewer potential image artifacts.
Live grading software is highly recommended in order to provide real-time control over the image when viewing HDR on-set. Most software options support both camera native color management and ACES color management.
If Live Grading Software is not being used, or crew is not available to run such software, some options for HDR Monitoring include:
In-Camera Output or LUT
Some cameras offer the ability to use their own color management to directly output for HDR on-set monitoring. See our camera guides in Cameras and Image Capture for more information.
In-Monitor LUT
If there are limitations with in-camera color management, some monitors offer the ability to load LUTs directly or apply color processing internally, allowing the camera to send a log signal directly to the monitor for image processing.
Appendix
Traditional LCD Panel Types:
LCD stands for liquid crystal display. LCDs are a panel technology that utilizes a backlight and an LCD layer that modulates the light to create a color image. LCD technology is common among SDR displays and mobile devices because of its low cost and decent image quality.
However, since the LCD layer has to ‘block’ the backlight that is always on, it is difficult to produce the deep black levels necessary for HDR. Also, because the LCD layer uses polarization to block or allow light to get through, LCDs suffer from limited viewing angles. This means color and luminance may vary perceptibly depending on the angle at which the LCD screen is viewed, potentially creating problems in an on-set environment.
Local Dimming LCDs:
In order to help LCDs produce HDR images, a backlight technology called ‘local dimming’ is often used. This utilizes multiple backlight ‘zones,’ which can individually turn on and off in order to increase the effective dynamic range of the image. When there is a dark area of the frame, the backlight zones in that area can dim or turn off to produce a pure black. In bright areas of the frame, those zones can turn on to help produce specular highlights.
While local dimming is almost always a good thing, the number of zones and the dimming algorithm can have a significant effect on the viewing experience. Good local dimming can effectively increase the dynamic range of LCD displays, but the added cost of additional backlights and the dimming algorithm needed can have an exponential effect on the cost of the display. Less expensive displays often achieve their lower cost by including too few backlights and/or employing an inadequate dimming algorithm, which can lead to display issues such as “blooming” or “halo” effects where there is a perceptible backlight glow around high contrast areas such as small bright objects or white text over black.
Global Dimming LCDs:
Some products, which lack local dimming capabilities, utilize a technology called ‘global dimming.’ This means that during a dark shot, the entire backlight is dimmed and during a bright shot, the entire backlight is turned up. Global dimming can have serious negative implications for on-set HDR reference monitor use. With both SDR and HDR monitoring, one of the most common workflows on-set is to ‘lock off’ the camera on a scene and adjust lighting based on a static image. Because the entire backlight is changing dynamically based on image content, a global dimming display is particularly unreliable on static images, providing little to no consistency from set up to set up.
Dual-Layer LCDs:
Image courtesy of Flanders Scientific Inc.
Dual-layer LCDs, sometimes referred to as ‘dual-cell’ LCDs, utilize two layers of LCD in front of the backlight. Dual-layer LCDs avoid the need for local dimming. While one of the LCD layers is used to modulate the overall luminance, the second LCD layer introduces the color subpixels. This separates the tasks of light and modulation to provide a fairly reliable, stable image.
OLED:
OLED stands for organic light-emitting diode. Compared to LCD displays, where there is a backlight producing light and an LCD layer modulating it, OLEDs have the advantage of each individual pixel in the display being able to turn on or off to produce light or black. This means that OLEDs can produce near-perfect black levels with better viewing angles than LCDs.
NOTE: Not all monitors that claim to be HDR are actually HDR. When planning an HDR on-set workflow, beware of “BSDR” or “Bright SDR” monitors. These products are often marketed as “HDR-capable” because they can interpret an HDR signal type. While some of these BSDR displays can get as bright as HDR monitors, the dynamic range is still as limited as an SDR monitor and the technology itself should still be considered SDR.
Glossary
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