How ISO 21496-1 unites HDR photos across Android and iOS devices

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A person holding the iPhone 16 and the Pixel 9.
It's great that Android supports HDR (High Dynamic Range) photography, it's a big leap forward allowing true HDR capture using Google’s Ultra HDR image format. However, this initially faced a compatibility hurdle across different platforms, particularly between Android and iOS.

The good news is that it's being resolved, as both Google and Apple are now adopting a unified standard for HDR gain map metadata, ensuring images display as intended on any device, Android Authority reports.

Unlike previous techniques that simulated HDR by blending multiple photos, Ultra HDR uses a single capture to achieve a realistic dynamic range.

Ultra HDR's design is innovative, as it’s based on the commonly used JPEG format instead of creating a whole new file type. Ultra HDR images are simply JPEGs with additional metadata that includes a gain map. The gain map is key – it’s an overlay of brightness and color adjustments that transform the JPEG into an HDR image when viewed on compatible devices.

Devices or apps that support HDR can apply the gain map to show the enhanced version, while others without HDR support display a standard SDR (Standard Dynamic Range) version.

One challenge for app developers has been the variety of ways to encode gain map metadata. For example, Google’s Ultra HDR uses Adobe’s encoding method, while Apple has developed its own. Not good in terms of practicality.

Apps that want to display HDR photos consistently across Android and iOS devices would need to manage and potentially convert between these different formats. To address this issue, Google and Apple are now turning to the ISO 21496-1 standard, which provides a unified method for encoding gain map metadata and makes HDR photos fully cross-compatible across platforms.



With the ISO 21496-1 standard, devices can capture, share, and display HDR photos without compatibility issues. For instance, an HDR photo taken on an Android phone can now be sent to an iPhone, iPad, or MacBook, and it will appear in full HDR, and vice versa. This cross-platform compatibility has the potential to make HDR photography much more accessible, letting users capture and share high-quality images without worrying about whether the recipient's device will display it correctly.

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To make this cross-compatibility a reality, devices and apps need to implement the ISO standard. Apple announced at its recent WWDC event that new APIs for reading and writing gain map data will be available in macOS 15, iOS 18, and iPadOS 18.

Core Apple apps like Messages, Photos, and Preview have already begun incorporating ISO 21496-1 support. Some users have even noted that HDR photos taken on Google Pixel devices display correctly on recent MacBook models, suggesting that Apple may have already implemented support for Ultra HDR’s gain map encoding.

Google has also expanded Ultra HDR’s reach, integrating ISO 21496-1 support into its latest Android 15 release, which now encodes both Ultra HDR’s native metadata and the ISO standard. This dual encoding approach means that Ultra HDR photos captured on Android 15 devices are viewable in HDR across different platforms and apps, including Google Chrome, which now also supports ISO 21496-1.

Already, the Google Photos app on Android is compatible with HDR photos from iPhones, and Apple’s Messages and Photos apps have started supporting HDR files from Google devices. As more platforms adopt ISO 21496-1, HDR compatibility between Android and iOS will continue to improve, making it easier than ever to capture and share HDR photos that look stunning, no matter the device.

This is great news, folks. We should all see "the same" images across different devices!

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