How AVIF Handles HDR Imagery Compared to SDR Formats

The AV1 Image File Format (AVIF) represents a generational leap in digital imaging by natively supporting High Dynamic Range (HDR) workflows that traditional Standard Dynamic Range (SDR) formats cannot match. Utilizing compression technology derived from the AV1 video codec, AVIF handles high peak brightness, deep black levels, and wide color gamuts by implementing 10-bit and 12-bit color depths along with modern transfer functions like PQ and HLG. Compared to legacy SDR formats such as standard JPEG and WebP—which are constrained by 8-bit limits and narrow color spaces—AVIF preserves realistic luminance and fine color gradients while maintaining remarkably low file sizes.

Bit Depth and Gradient Precision

Standard SDR formats like JPEG and WebP are typically restricted to an 8-bit color depth per channel. This limits each pixel to 256 values per color channel (roughly 16.7 million possible colors). When rendering scenes with extreme brightness or subtle gradations—such as sunsets or shadows—8-bit formats frequently suffer from posterization and visible color banding.

AVIF natively supports both 10-bit and 12-bit color depths. A 10-bit depth provides 1,024 values per channel (over 1 billion colors), while 12-bit offers 4,096 values per channel. This exponentially larger numerical range allows AVIF to capture the broad brightness spectrum required for HDR without introducing banding artifacts or losing detail in dark and bright extremes.

Electro-Optical Transfer Functions: Gamma vs. PQ and HLG

SDR formats rely on conventional gamma curves (such as sRGB) originally designed for cathode-ray tube (CRT) monitors. These curves assume a maximum display brightness of around 100 nits, discarding highlight and shadow data beyond this narrow range.

AVIF integrates modern Electro-Optical Transfer Functions (EOTFs) specified by the ITU-R BT.2100 standard:

• Perceptual Quantizer (PQ / SMPTE ST 2084): Designed to match human visual perception across a luminance range reaching up to 10,000 nits. This allows AVIF to encode intense specular highlights—such as reflections on chrome or direct sunlight—alongside deep shadow details.
• Hybrid Log-Gamma (HLG): A curve that offers backward compatibility with SDR displays while providing expanded dynamic range on supported HDR screens.

Wide Color Gamut (WCG) Support

Most SDR images are bound to the Rec. 709 / sRGB color space, which represents only about 35% of the colors the human eye can perceive.

AVIF features full support for wide color gamuts, notably DCI-P3 and BT.2020. BT.2020 covers approximately 75% of the visible spectrum. Because HDR requires both high luminance and rich, saturated colors at extreme brightness levels, AVIF’s native support for these broad color profiles ensures that bright highlights retain their true color rather than blowing out into pure white.

Tone Mapping and Auxiliary Gain Maps

To manage differences in display capabilities, AVIF supports HDR metadata detailing mastering display color volumes (MDCV) and content light levels (CLL). This informs the rendering device precisely how to tone-map the image according to the screen’s maximum luminance.

Additionally, AVIF supports multi-layer architectures and auxiliary gain maps (such as the ISO 21496-1 standard). In this approach, a baseline SDR image is paired with a lightweight monochrome or color gain map within a single AVIF file. Standard displays render the baseline SDR layer without distortion, while HDR-compatible displays use the gain map to scale the brightness and color up to full HDR, solving the cross-platform backward compatibility problem that previously hindered HDR image adoption.