Drop a JPEG to see whether it carries an HDR gain map, compare it with the SDR version, and save a standard JPEG for print or posting.
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DetailsDrop JPEG photos here, or click to choose
You can select several files at once. JPEG only.
What Is an Ultra HDR Gain Map, and When Should You Remove It?
Many recent phones save photos as Ultra HDR JPEGs. The file looks like a normal JPEG, but it also carries a gain map: a second image that tells an HDR-capable screen how much brighter each area should be. Apps that don't read the gain map show only the standard SDR image, so the same file can look different depending on where you open it.
Drop a JPEG here to see whether it has a gain map. If it does, you can drag a slider to compare the SDR image with a simulated HDR version, then save a plain SDR JPEG with the gain map removed. Everything runs in your browser.
The tool also shows basic camera info from the photo's EXIF data, such as the camera model, date taken, aperture, shutter speed, ISO, and focal length.
Where Gain Map JPEGs Cause Problems
Posting to social media
If you aren't sure how an app treats HDR photos, save an SDR copy first so every app starts from the same image.
Ordering prints or a photo book
Prints are made in SDR. Check how the photo looks without the gain map and upload the SDR version instead of the original.
Publishing photos on a website
A plain SDR JPEG doesn't depend on gain map support, and removing the gain map image usually makes the file smaller.
Cleaning up a batch of trip or event photos
Add many files at once. Photos with a gain map are converted, and you can download them one by one or all together.
How to Remove a Gain Map from a JPEG in 4 Steps
- Drop your JPEG photos into the box, or click it to choose files. You can select several at once.
- Read the result for each photo: gain map found, possible gain map, or none. Open Camera info to see EXIF details.
- Click Compare with HDR preview and drag the slider to see the SDR image next to the simulated HDR version. Use the boost setting to change how bright the preview gets.
- Choose Keep metadata or Re-encode, click Convert, then download the SDR JPEGs.
Note: Everything runs in your browser. Your photos are not uploaded.
Limits of the Gain Map Check and HDR Preview
- JPEG only: HEIC, PNG, and WebP files are skipped. The check works on photos where the gain map is stored inside the JPEG file.
- How detection works: the tool reads the file's XMP metadata for gain map tags and looks for a second JPEG after the main image. A second image without tags is reported as a possible gain map. It is not a full parser for every gain map container.
- The HDR preview is a rough simulation. It brightens the photo using the gain map, then clips at white. It needs the gain map settings to be in the file, and it uses a single brightness channel of the gain map.
- Re-encode mode saves a new JPEG through your browser's canvas. EXIF and the embedded color profile are not carried over, so colors in wide-gamut photos may shift slightly.
- Keep metadata removes the XMP block that holds the gain map tags. If other XMP data, such as edit history, is stored in the same block, it is removed too.
- Very large photos and big batches take longer to analyze and convert.
Keep Metadata vs. Re-encode: Which SDR Mode to Choose
Both modes produce a JPEG without a gain map. They differ in what else is kept and in how the file is written.
| Keep metadata | Re-encode | |
|---|---|---|
| Image data | Main image copied unchanged | Redrawn and compressed again |
| EXIF (camera, date taken) | Kept | Removed |
| Color profile | Kept | Not carried over |
| Gain map image and its tags | Removed | Removed |
| Quality setting | None, no recompression | 30 to 100, default 85 |
| Speed | Fast | Slower for large photos |
| Good for | Archiving, or sharing with camera info | Public posts where you want EXIF gone |
If Keep metadata reports that gain map data is still in the file, switch to Re-encode. It writes a new file from the visible image, so nothing from the original container is left.
How the HDR Boost Is Stored, and Whether to Keep It
A short guide to what is inside an Ultra HDR file and how to decide between the original and an SDR copy.
What the file contains
An Ultra HDR JPEG holds the standard SDR photo plus a second image, the gain map. Where the map is bright, an HDR-capable screen lifts the SDR pixel more. Where it is dark, the pixel stays close to its SDR value.
The file also stores the minimum and maximum boost, in stops, and the range of display brightness the map was made for. A viewer uses these numbers to scale the effect to the screen it is running on.
When to keep the gain map
Keep the original when you view or share the photo on screens and apps you know support HDR gain maps. That is where the extra highlight detail shows up. Keep a copy of every original even if you also make SDR versions.
When to remove the gain map
Make an SDR copy when the photo is going to print, to a website, or to a service you can't check. The SDR file has no second image to interpret, so it does not depend on how an app handles gain maps.
A simple workflow
Store the phone original as your master. Use this tool to export SDR JPEGs for publishing, and keep the two sets in separate folders so you can always go back to the HDR version.
Common HDR Export Mistakes
Sending an HDR photo to print without checking it
A photo that looked great on your phone can come back from the printer with different highlights or overall brightness, because prints are made in SDR.
💡 See the solution▼
Posting the same photo and getting different looks in different apps
Apps that read the gain map and apps that ignore it can show the same file with different highlights, so people see different versions of your photo.
💡 See the solution▼
Putting gain map JPEGs on a web page without checking file size
The gain map is stored inside the file, so it adds to the file size. A page full of these photos can load more slowly.
💡 See the solution▼
Deleting the original after converting
If you overwrite or delete the HDR original, you can't get the HDR version back later.
💡 See the solution▼
Questions About Gain Maps, EXIF, and Privacy
Q.What is a gain map in an HDR photo?
A. A gain map is a second image stored inside the same JPEG file as the normal photo. It is usually grayscale and records how much brighter each area should be on an HDR-capable screen. Apps that support it use the map to lift highlights. Apps that don't support it show only the standard SDR image.
Q.How can I tell if my photo has a gain map?
A. Drop the JPEG into the tool. It reads the file's XMP metadata for gain map tags and looks for a second JPEG stored after the main image. If it finds tags, it reports a gain map. If it finds only a second image with no tags, it reports a possible gain map. When the settings are in the file, it also shows the maximum boost in EV and the gain map version.
Q.Why does my HDR photo look different on some sites, apps, or in print?
A. Apps handle gain maps in different ways. Some show only the SDR image, some brighten highlights on HDR screens, and print services work in SDR. The same file can therefore look different from one place to the next. An SDR copy contains one image and no gain map, so every app starts from the same picture.
Q.Is the HDR preview the same as seeing the photo on an HDR display?
A. No. The preview applies the gain map to the SDR pixels to estimate how much brighter the highlights would get, then clips anything above white because a standard screen can't show more. It uses a single brightness channel of the gain map and needs the gain map settings to be present in the file. For an accurate look, open the original on an HDR display in an app that supports gain maps.
Q.Will the converted JPEG keep its EXIF data?
A. It depends on the mode. Keep metadata copies the main image unchanged and removes the gain map image, the XMP block that describes it, and the MPF block that points to it. EXIF data and the embedded color profile stay. Re-encode redraws the image and saves a new JPEG, so EXIF and other embedded metadata, including the color profile, are not carried over.
Q.Are my photos uploaded anywhere?
A. No. Detection, the preview, and the conversion all run in your browser, and the photo files are never sent to a server. You can use it on photos you haven't shared yet.
Q.Can I convert HEIC, PNG, or WebP files?
A. No. The tool reads JPEG files only, and other formats are skipped with a message. It looks for gain maps stored inside a JPEG, which is how Ultra HDR photos are saved.
Q.Can I convert several photos at once?
A. Yes. Add as many JPEGs as you like. Only files with a gain map are converted. You can download each result separately or all at once. When you download several files, your browser may ask for permission to allow multiple downloads.
Q.Will the SDR file be smaller than the original?
A. In Keep metadata mode the gain map image is removed, so the file is usually smaller. In Re-encode mode the size depends on the quality you choose and can be larger or smaller. After converting, the tool shows the size of each file and the overall change.
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