Camera RAW
What is an X3F file?
Updated Jul 2026
X3F is the RAW file format used by Sigma digital cameras, closely tied to Sigma's Foveon sensor technology. It stores the unprocessed data captured straight off the sensor, so no detail is thrown away during shooting. The tradeoff is that very few programs outside Sigma's own software can open it directly.
- Extension
- .x3f
- Type
- Camera RAW
- Typically
- Sigma cameras
- Metadata
- Carries EXIF
Why X3F exists
Sigma introduced X3F to go along with its Foveon X3 sensor, a design that differs from the Bayer sensors most other camera makers use. Instead of guessing at color through interpolation, a Foveon sensor captures red, green, and blue at every single pixel location, and X3F is the format built to hold that raw output.
Because it stores everything the sensor recorded, an X3F file is lossless: nothing gets compressed away or approximated. It also carries the shooting metadata, things like exposure, ISO, and lens settings, alongside the image data. That completeness is exactly why the files are large and why processing them takes real computing effort.
The problem people run into is compatibility. Photo viewers, browsers, and most editing programs don't recognize X3F at all, so a photographer usually has to convert it to something like a TIFF, DNG, or JPG before they can edit it, share it, or even just look at it.
The trade-offs
Strengths
- Lossless: keeps the full data captured by the sensor
- Foveon capture means full color info at every pixel, not interpolated
- Retains complete shooting metadata alongside the image
- Gives editors the most latitude to adjust exposure and color later
Watch-outs
- Very few programs outside Sigma's own tools can open it
- Large file sizes compared to a finished JPG
- Slower to process because of the sensor's unusual data layout
- Can't be viewed in a browser or most photo apps without converting first
A note on privacy
An X3F file carries EXIF metadata like camera settings, lens data, and timestamps, and sometimes location if the camera has GPS. Uploading it to an online converter sends all of that, along with the full-resolution image, to someone else's server. Converting on your own machine keeps the photo and everything attached to it on your computer.
Questions
How do I open an X3F file?
You'll generally need Sigma's own software or a RAW editor with Foveon support. Most people convert it to a TIFF or JPG first so it opens in ordinary photo viewers and editors.
Is X3F better than DNG?
X3F preserves Sigma's unique Foveon sensor data more faithfully, but DNG is far more widely supported. Many photographers shoot in X3F and convert to DNG once they're ready to edit in mainstream software.
Why does my Sigma camera save photos as X3F?
It's Sigma's native RAW format, built specifically to store the full, unprocessed output of its Foveon sensors. Shooting in X3F preserves the most detail for later editing.
Can I convert X3F without uploading it?
Yes. A desktop app like Morphjet converts X3F files on your own computer, so the image and its embedded camera and location data never leave your machine.
Morphjet opens and converts X3F and 1,800+ other formats, all on your own computer. Launching this July.