What is Ultra HDR?
One file, two renditions: a normal photo, and a brighter one for screens that can show it.
In short
Ultra HDR is an image format introduced with Android 14. It is a standard JPEG followed by a small second image, the gain map, which tells an HDR screen how much brighter each area may be. Apps that do not understand the format show the normal JPEG; compatible ones — Chrome, recent Android — show the brighter version.
Key takeaways
- A normal JPEG plus a gain map in the same file.
- Fully backwards compatible: nothing breaks on older screens.
- The brightness gain only shows on an HDR screen, in a compatible app.
SDR, HDR and the gain map
An ordinary photo — SDR, standard dynamic range — is made for screens of limited brightness. HDR screens can make highlights several times brighter than paper white: the sun on water, a lamp, a sky. The gain map records, area by area, how much brighter the HDR rendition should be than the SDR one.
Ordinary JPEG
displayed everywhere
Gain map
how much to brighten each area
HDR on HDR screens
Why one file instead of two
Sending a separate HDR image would break on every device that cannot read it. Ultra HDR avoids that: the first image is a complete, ordinary JPEG, and the gain map is stored after it with a short description. Software that does not look for it never sees it.
Where it shows
- Chrome on an HDR screen displays Ultra HDR images in HDR.
- Android 14 and later shoot and display Ultra HDR photos.
- iPhone photos also use a gain map, in Apple’s own format; how other gain map formats are shown varies from app to app.
Making one from an ordinary photo
A converter can create a gain map from an SDR photo by boosting its brightest areas. This does not recover detail that was never captured, but it gives highlights the extra brightness that HDR screens are able to show.
HDR image converter: JPG to Ultra HDR
Give your highlights real brightness on HDR screens, while keeping a normal JPEG for everyone else.
Open the tool