Mobile photography enthusiasts know that HDR on Android and iOS are completely different technologies. But now Google and Apple have adopted a new common HDR standard, ISO 21496-1, which should eliminate the differences. Android Authority writes about it.
Google has developed the Ultra HDR format, which is essentially an improved JPEG. An additional bit of metadata is superimposed on the image. This metadata takes the form of a gain map, which, when applied over the base image, turns it into an HDR photo. Devices and programs that support HDR and know how to apply the enhancement map will "see" HDR version of the photo, while everyone else will see the SDR version of the photo.
The problem for applications is that there are several ways to encode gain map metadata in an image file. Google's Ultra HDR uses Adobe's encoding scheme, but Apple has its own version of this technology.
This means that platforms like Instagram must not only work with both methods, but also convert images between them if they want Android and iOS devices to see any HDR photo the same way.
To solve this problem, companies have adopted a single standard for metadata for the gain map - ISO 21496-1. It standardizes how gain map metadata and its attributes are defined and applied. When applied correctly, the standard allows HDR photos to be created and shared across platforms. By the way, the Google Photos app on Android already supports HDR photos taken on an iPhone.