Google Photos Gets A Great New Tool To Make Your Photos Pop
The Ultra HDR format enhances brightness, contrast, and color. It combines standard dynamic range (SDR) with high dynamic range (HDR) data into a single file. This means photos will look more vibrant on devices supporting HDR while still appearing normal on those that do not.
Before now, converting an SDR image to HDR was a relatively complex process and not easily accessible to consumers. It involves shooting in HDR from the start. However, with newer image processing techniques, Google is now able to upgrade SDR images to HDR. To enjoy this feature, though, Google will have to update your app and include the option from its end.
To use the new feature, open any photo in Google Photos app, tap "Edit," and select "Adjust". If you've received the update, the previous "HDR effect" option will be replaced with “Ultra HDR.” Once applied, the photo will display richer colors and deeper contrast if you use a newer Android phone that has an HDR display.

The Ultra HDR format was introduced with Android 14 and is supported by phones with HDR-capable screens. It uses a “gain map” to brighten or enhance specific parts of the image without drastically increasing the file size.
If you've updated your app but still haven't seen the feature, be patient -- it should be available soon.