How to use it
- Upload a JPEG, up to 1600 pixels on the long side.
- Leave it on automatic, or switch to manual and paint the areas you want brighter.
- Download the file and open it on a phone with an HDR display.
What it looks like on an HDR screen
Simulated. On the screen you are reading this on, both halves are identical — an ordinary display has no extra brightness to give. This is how the difference reads on an HDR display.
What the converter actually builds
Both images above are real output from this converter, not an illustration. White areas of the gain map are the ones an HDR screen brightens; black areas stay exactly as they were.
Frequently asked questions
What is Ultra HDR?
A JPEG that carries a second, hidden image called a gain map. HDR displays multiply the visible picture by that map to reach brightness beyond ordinary white. Displays that do not know the format simply ignore it.
Does the converted file still open everywhere?
Yes. The base image is an ordinary JPEG, so anything that opens a photo opens this. Backward compatibility is the whole design of the format.
Will my picture just look brighter overall?
No, and that is the difference between this and raising exposure. The threshold is chosen from your own image so only the brightest quarter of it is eligible. If a photo has no highlight structure at all, a flat white background for example, the converter says so instead of lifting everything.
Is quality lost?
The base image is re-encoded once at quality 95, which is visually lossless for normal viewing. The gain map is stored separately and does not touch the detail of the original.