About color space

No image device is capable of capturing and displaying the full spectrum of colors visible to the human eye. Consequently, image devices record, edit, display, or output a subset of those colors. This range of reproducible color is known as the device’s color gamut. Additionally, devices capture, process, and display different ratios between the lightest and darkest parts of an image, from pure black to brightest white. This luminance range is known as dynamic range. Together, these attributes define an image’s or device’s color space.

Standard-gamut versus wide-gamut color

Traditional computer displays and HDTVs support a limited color space that’s based on a decades-old industry standard called Rec. 709. Rec. 709 devices (and the video content created for display on them) have standard-gamut color, the constrained color palette you see whenever you view a broadcast HDTV show, DVD, or Blu-ray disc.

A more recent generation of displays—including 4K TVs and computer displays, Apple TV 4K, and newer Mac, iOS, and iPadOS devices—can render a much wider palette of colors. These wide-gamut color devices display more vivid and lifelike hues (in addition to all the hues that standard-gamut devices can display). Accordingly, the video industry has adopted a wide-gamut color standard called Rec. 2020.

SDR versus HDR

Older displays and TVs are also limited in the levels of brightness they’re capable of reproducing, known as their dynamic range.

Standard dynamic range (SDR) is the conventional imaging approach that captures, processes, and displays a narrow range of luminance values (levels of brightness) and color values. SDR can represent a maximum luminance value of around 100 nits (candelas per square meter) and a dynamic range of 6 to 10 stops.

High dynamic range (HDR) imaging captures, processes, and displays a much wider range of luminance and color values. HDR can represent luminance values as high as 10,000 nits and a dynamic range of 14 stops or more.

HDR displays typically process video at 10 or 12 bits per color component rather than 8 bits. The additional data lets HDR displays render more discrete steps from the minimum to maximum brightness value in each color, creating more realistic color transitions and revealing more detail in both shadows and highlights.

A simulated split-screen image comparing SDR and HDR.

There are multiple HDR formats, including HDR10, Dolby Vision, Hybrid Log-Gamma (HLG), and Perceptual Quantizer (PQ). Although PQ can represent luminance levels of up to 10,000 nits, no display is capable of showing such levels. As a result, HDR content must be mastered with a lower peak brightness, usually around 1,000 nits. All common formats require HDR be delivered with wide color gamuts.

HDR imaging requires preservation of luminance and color data throughout the production pipeline: Images or clips must be captured on a device capable of recording HDR-level color and luminance ranges, stored and distributed with their HDR data intact, then displayed on a monitor capable of converting that HDR data to corresponding light values onscreen using a mathematical formula called a transfer function. If a monitor isn’t capable of displaying HDR, tone mapping is applied to restrict the wide range of luminance values in HDR images to the narrower range of brightness values supported by an SDR display.

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Motion User Guide

About color space

Standard-gamut versus wide-gamut color

SDR versus HDR