.x3f File Extension

What kind of file is a .x3f?

An .x3f file is a RAW photograph created by Sigma and Foveon digital cameras. It can contain raw sensor measurements, one or more rendered previews, and camera properties in a single binary container. That gives a RAW editor more latitude over white balance, exposure, noise reduction, and sharpening than a finished JPEG provides.¹

X3F usually uses the conventional image/x-sigma-x3f MIME type, but that media type is not registered with IANA.² An actual X3F begins with the ASCII signature FOVb, or 46 4F 56 62 in hexadecimal. Checking those bytes is more reliable than trusting the name.

How do I open a .x3f on my computer?

SIGMA Photo Pro is the safest first choice on Windows or macOS. Sigma describes it as software for displaying and manipulating RAW images from all Sigma digital cameras, and current releases still handle X3F files.³

Adobe Camera Raw and Lightroom also open X3F captures from listed Sigma models. Check Adobe's camera table because compatibility depends on the camera and minimum software version, not only the extension.⁴ Sigma also offers a Photoshop X3F plug-in for selected Merrill and Quattro cameras, but directs owners of some older models to Camera Raw instead.⁵

Web browsers do not natively display X3F. Export a JPEG for convenient viewing or sharing, while retaining the original .x3f file for future RAW adjustments.

Poly support for .x3f

Poly gives X3F photos thumbnails, an in-app image preview, supported camera metadata, visual search, and agent understanding. You can find a capture by filename, color, or visual similarity, and the Poly agent can reason about the visible photograph.

Poly presents a rendered view rather than a RAW-development workspace. Use a compatible RAW editor for sensor-level adjustments. Words photographed in an X3F are not indexed as document text, and original files can contain identifying camera, owner, serial, timestamp, lens, or location metadata. Review metadata before sharing.⁶

History of .x3f

The .x3f extension belongs to Foveon's X3 image workflow. Sigma introduced the SD9 camera in October 2002, and its manual specifies .X3F filenames for captured images.⁷ The camera paired a Foveon X3 three-layer sensor with losslessly compressed 12-bit RAW recording.⁸

Foveon's surviving external format specification begins its revision history in January 2003. It documents the container, previews, thumbnails, and properties, but leaves some image encodings outside the public specification.¹ That partial documentation helps explain why support can vary across camera generations.

Working with .x3f and alternatives

Choose an export based on what happens next:

An exported file preserves one interpretation of the capture. It does not retain every adjustment available from the source, so keep the original X3F even after producing JPEG or TIFF derivatives. If you convert to DNG, validate representative files before changing an archival workflow.