HDR Photo
What’s HDR
Essentially, HDR is a set of technologies designed to present the visual world around us with higher fidelity. It allows a wider range of light intensities in real life to be captured and displayed. It can display a deeper range of colors compared to standard dynamic range. It also defines a set of rules or transformations that can display brighter and deeper content on an HDR screen. These transformations are called tone mapping.
What is tone mapping, you might ask? To understand this, we first need to understand the concept of headroom.
To understand headroom, we need to talk about dynamic range in photography.
One of the amazing properties of the human visual system is the ability to adapt to a wide range of input stimuli, from the dim light of the night stars to the extreme brightness of the sun.
The term dynamic range refers to the contrast between the brightest and darkest tones of an image.
On a standard dynamic range display, you can only accurately present part of the real range of lighting. Although the image looks good, the image range is tonal compressed. On the other hand, HDR displays can present dark and bright tones better than SDR, with fewer compromises.
For example, specular highlights. Or the light from luminous objects is better preserved. The peak brightness that HDR can represent can be much higher than the SDR peak. According to the ISO image standard, the brightest SDR signal is also called reference white. Reference white is about the brightness of a page in a book in an indoor environment, or the white background of a Keynote presentation.
On the other hand, HDR displays allow us to render specular highlights or light from shiny objects brighter than reference white. The extra brightness is called headroom.
HDR Photo Standards
As of 2025, the formats and standards for high dynamic range (HDR) photos have evolved significantly. The main HDR photo formats and their associated standards are as follows:
| Format | Description | Compatibility | Reference |
|---|---|---|---|
| HEIC(HEVC encoding in HEIF format) | An image format that supports HDR and uses HEVC encoding with high compression efficiency | Widely supported, including Apple devices and some Android devices | |
| AVIF (AV1 encoding in HEIF format) | An image format based on AV1 encoding that supports HDR and provides efficient compression performance. | Gradually supported by more platforms and browsers | |
| JPEG XR | A format developed by Microsoft that supports high dynamic range images and better compression performance | Used in certain professional apps and in the Microsoft ecosystem | |
| JPEG XL | A next-generation image format that supports HDR and is designed to replace traditional JPEG, providing more efficient compression and richer features | It is being gradually adopted and is expected to become mainstream in the future | |
| HSP (CTA 2072 HDR Still Photo Interface) | Format used by Panasonic cameras for HDR photo capture using the HLG transfer function | Used primarily in certain Panasonic cameras and display devices | |
| ISO 21496-1 Gain Map | A standard jointly proposed by Adobe and Apple that enables HDR display by adding a conversion layer on top of SDR data while maintaining compatibility with SDR displays | Called Adaptive HDR by Apple, supported platforms include macOS 15, iOS 18, iPadOS 18, Android 15, and Chromium-based browsers | |
| Apple HDR | Apple’s private implementation, HDR information added on top of SDR images | Supported in Apple devices and software, but not fully publicly documented | |
| Adobe Gain Map (Ultra HDR, Super HDR) | Adobe’s gain map method is called Ultra HDR by Google and Super HDR by Samsung | In Android 15, Ultra HDR and ISO 21496-1 formats are encoded simultaneously and will gradually be supported by more devices | |
| Apple EDR (Extreme Dynamic Range) | Technology used by Apple in macOS and iOS that allows SDR and HDR content to be displayed on the same screen | Mainly used on Apple devices | |
| OpenEXR | An open source high dynamic range image format created by Industrial Light & Magic (ILM) and widely used in film and television production | Used in professional fields, especially in visual effects and animation production | |
| ACES（Academy Color Encoding System） | A complete color and profile management system created by the Academy of Motion Picture Arts and Sciences with support for HDR and wide color gamut | Standard workflow in professional film production |
The above various standards can be summarized into 2 categories:
- PQ HDR photos with native brightness information, such as AVIF, HEIC
- Gainmap HDR photo achieved by adding a gain map
Gainmap is also a gray image. On supported screens, add extra brightness to the white part of the gainmap (i.e., highlights) to achieve the effect of HDR lighting.
HDR Photo Examples
I exported HDR photos in various formats from the RAW photos I shot with my camera.
| 说明 | JPG | AVIF |
|---|---|---|
| PQ |  700KB |
 372KB |
| Adobe Adaptive Color |  1.3MB |
 393KB |
| Apple HDR |  1.5MB |
|
| Adobe Adaptive Color Maximized Compatability |
 1.8MB |
 1.0MB |
| Adobe Adaptive Color no Maximized Compatability |
 1.6MB |
 324KB |
| Adobe Color Maximized Compatability |
 1.4MB |
 863KB |
| Adobe Color No Maximized Compatability |
 1.3MB |
 323KB |
How to Choose
From my personal experimental results, Apple HDR is currently the most compatible format, and HDR effects can be displayed normally on supported iOS/Mac OS/Android devices.
If you want to save it to the photo album and watch it later, then:
Use Camera RAW Select Adobe Adaptive Color Select None Maximized Compatibility Export AVIF to get the best HDR photos.
The advantages of this configuration export are:
- 10 Bit, there is still room for post-production, and there will be no discontinuity in color transition
- The volume is very small and the image quality is also very good
- This AVIF can still be recognized as an HDR photo when put into Camera RAW, and the HDR effect can be re-edited
- HDR display can be correctly activated on iOS/Mac OS (iOS Safari cannot)
What about JPG?
- Apple HDR has the best jpg compatibility. Apple HDR was launched on iPhone 12. Now it has been several years and most software supports it. You can convert photos to Apple HDR through Photomator, but the brightness of HDR photos converted by Photomator is directly maxed out, and the color and appearance are not normal
- The HDR photos taken by the new iOS are now called Apple Adaptive HDR, which is ISO 21496-1 HDR
- ISO 21496-1 HDR photos taken by iPhone can be displayed in the browser on supported devices, but ISO 21496-1 HDR photos exported through Camera RAW cannot trigger HDR brightness on iOS Photos. The Gainmap exported by Camera RAW is Multichannel, while that of iPhone is Single Channel
- At this stage, JPG photos with HDR cannot retain the HDR gain map when edited again in other software except Photos
HDR Related Softwares
- Photos
- Photomator
- Camera RAW
- https://github.com/grapeot/AppleJPEGGainMap
- https://github.com/chemharuka/toGainMapHDR