What is Ultra HDR?
Ultra HDR is a photo format that makes the bright areas of an image physically glow on HDR screens — while staying a normal JPEG everywhere else. It's the gain-map standard behind the HDR photos on modern iPhones, Android phones, Instagram and Google Photos. Here's exactly what it is and how it works.
See the difference
Ultra HDR in one sentence
An Ultra HDR file is an ordinary JPEG with an extra layer baked in: a gain map. The base image is the standard photo every screen can show; the gain map is a grayscale instruction that tells HDR-capable displays how much brighter to render each pixel. On an HDR screen, highlights — the sun, neon, reflections — shine beyond plain white. On any other screen, you just see the normal JPEG.
How the gain map works
The gain map is a per-pixel multiplier. Where it's dark, the display shows the base brightness; where it's bright, the display lifts that area into the extra brightness range (the HDR 'headroom') the screen has available. Because the boost is stored as a separate map, the same file looks correct on both SDR and HDR screens — no clipping, no broken colors. MakeHDR computes this gain map from your photo's own luminance, in 32-bit float, with no AI and no invented detail.
Ultra HDR vs HDR10 and Dolby Vision
HDR10 and Dolby Vision are video standards — they describe HDR for movies and TV. Ultra HDR is the photo equivalent: a still-image gain-map format standardized as ISO 21496-1, with Adobe's gain-map XMP. Google introduced the name 'Ultra HDR' on Android; Apple uses the same ISO gain-map approach for iPhone HDR photos. So a single Ultra HDR JPEG glows across Android, iOS and the web.
Where Ultra HDR photos display in HDR
Ultra HDR renders in HDR in Google Photos, the iOS Photos app, Chrome and Safari, and in apps that support it like Instagram. On phones and laptops with HDR screens — most modern devices — the highlights physically brighten. On older SDR screens, the embedded base JPEG shows normally, so nothing looks broken or washed out. That graceful fallback is why Ultra HDR is safe to use everywhere.
How to make an Ultra HDR photo
You don't need a 32-bit Photoshop pipeline or paid plugins. MakeHDR turns any finished JPEG, PNG or HEIC into a standards-compliant Ultra HDR file right in your browser — it computes the gain map locally from your image, with no AI and no upload. Drop a photo, pick the HDR strength, and download the Ultra HDR JPG.