Google and Apple find common ground in HDR standards

One of the best features of last year’s Android release was support for true HDR photos. Instead of layering photos or applying computational photography tricks to simulate HDR-like effects, phones running Android 14 and later use Google’s Ultra HDR image format to create true Capture HDR photos. While Ultra HDR was a huge advancement in mobile HDR photography, there was one major problem: lack of cross-platform compatibility. Thankfully, this is no longer an issue as both Google and Apple have adopted standards to display HDR photos as intended on Android and iOS.

The way Google designed Ultra HDR was very clever. Rather than create an entirely new format, Google created Ultra HDR based mostly on the widely supported JPEG format. In reality, Ultra HDR images are just JPEG files with additional metadata added. That metadata takes the form of a gain map that, when applied on top of the base JPEG image, turns it into an HDR photo. Devices and apps that support HDR and know how to apply gain maps will see the HDR version of the photo, while devices and apps that don’t support HDR or don’t understand gain maps will see the HDR version of the photo. The SDR version of is displayed. .

That’s the gist of how Ultra HDR works, but as anyone familiar with photography knows, things are much more complicated than that. One of these complexities concerns how the gain map metadata is actually encoded within the image. As we mentioned earlier, viewing an HDR version of an Ultra HDR image requires more than just having an HDR display on your device. You’ll also need to open the image in an app that recognizes the Ultra HDR gain map metadata and applies it on top of the base SDR image. Otherwise, only the base SDR version of the image will be displayed, even if your device has an HDR display.

The challenge for apps is that there are multiple ways to encode gain map metadata into image files. Google’s Ultra HDR, which uses Adobe’s encoding method, is one, but Apple has its own version. This means that if a platform like Instagram, for example, wants to display a particular HDR photo the same way on both Android and iOS devices, it not only has to handle both schemes, but also potentially convert between them. This means that there is. Fortunately, there is a better solution to this problem that has already been adopted by both Google and Apple. That’s the ISO 21496-1 standard for gain map metadata.

ISO 21496-1 standardizes how gain map metadata and its attributes are defined and applied. Proper implementation of this standard allows HDR photos to be captured and shared across platforms. For example, if you take an HDR photo on your Android smartphone and send it to a friend who has an iPhone, iPad, or Macbook, your friend will see the photo the same way you see it on your device. The same is true vice versa. Your friends can take HDR photos with their iPhones and send them to you to view on their Android smartphones and other devices.

However, for all this to be possible, devices must adhere to the ISO 21496-1 standard when encoding gain map metadata in images. Additionally, your app must be aware of ISO 21496-1 metadata.

Apple announced at WWDC that it is adding developer APIs to read and write gain maps using the ISO 21496-1 standard in macOS 15, iOS 18, and iPadOS 18. According to photographer Greg Benz, Apple’s Messages app, Photos app, Preview app, and Quick Look are adding support for the ISO standard. One user on Reddit pointed out that a 2022 14-inch MacBook Pro properly displayed HDR versions of photos taken with Pixel smartphones, suggesting that Apple has already rolled out support for the ISO standard in these four apps. The company has implemented support for the way Adobe/Google encodes gain map metadata.

After some testing and discussion with display analysts dylan ragaI concluded it’s the latter, but that doesn’t mean Google hasn’t also adopted the ISO 21496-1 standard. In fact, the Google Chrome browser already supports this, and the latest Android 15 release supports both encoding and decoding gain map metadata using the ISO 21496-1 standard. According to Google, Android 15 by default “encodes both Ultra HDR v1 metadata and ISO 21496-1 metadata when encoding Ultra HDR JPEG files.” This means that Android 15 smartphones that shoot in Ultra HDR will automatically output HDR photos that can be processed by other platforms. .

The Google Photos app on Android currently supports HDR photos captured from iPhones, but I’m not sure if that’s because Photos already supports the ISO 21496-1 standard. Much less do I know if the iPhone currently encodes gain map metadata using that standard. In any case, HDR photos are already cross-compatible between Android (if you use Google Photos) and iOS (if you use Apple Messages, Photos, or Google Photos), so both platforms have ISO 21496 Introducing -1 support only improves compatibility. Get HDR photos in even more apps and platforms.