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X3F converter

An .x3f file is a Sigma RAW photograph captured with a Foveon X3 sensor, which stacks three photodiode layers so every pixel location records red, green, and blue directly. That architecture makes .x3f fundamentally different from Bayer-pattern RAW files — there is no color mosaic to demosaic — and gives Foveon images their reputation for peculiar, film-like per-pixel sharpness.

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Drop X3F files here

Batch files can each use a different output. Nothing uploads for local conversions.

Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.

Where X3F comes from

Sigma launched the format with the SD9 DSLR in 2002, the first camera built around Foveon's layered silicon sensor, and later acquired Foveon outright in 2008. Merrill-generation sensors (2012) pushed the design's resolution, while Quattro models (2014) altered the layer resolutions, and Sigma has since shifted its L-mount cameras to conventional sensors, leaving X3F to the Foveon era.

How X3F works

  • Records three stacked layers per photosite, exploiting silicon's wavelength-dependent light absorption instead of a color filter array
  • No demosaicing step exists; instead, aggressive layer-separation math converts the stacked signals to RGB
  • Quattro sensors use a 1:1:4 layer arrangement — full-resolution blue layer over quarter-resolution green and red
  • 12-bit-per-layer data with relatively high noise in the deeper layers, limiting high-ISO usability
  • Container also stores previews, camera properties, and Sigma-specific processing parameters

When to use X3F

  • Base-ISO landscape, product, and architecture work where Foveon detail shines
  • Reprocessing archives from Sigma SD and dp-series cameras
  • Comparative study of non-Bayer color capture in imaging research

Strengths and limitations

Strengths

  • Per-pixel full color yields microcontrast and detail unlike any Bayer file
  • No color moire, since no mosaic pattern exists to alias
  • Distinctive tonal rendering many photographers find unreproducible elsewhere

Limitations

  • Third-party support is the weakest of any major RAW format; Sigma Photo Pro is often the only full-fidelity path
  • Layer separation amplifies noise, making files fragile above base ISO
  • Adobe Lightroom has never supported X3F natively, and LibRaw's Quattro handling has known limitations

Compatibility

Sigma Photo Pro, the free vendor application for Windows and macOS, remains the reference converter, while LibRaw-based tools (darktable, RawTherapee) decode Merrill-era files better than Quattro ones. Adobe's converters skip the format entirely, no OS previews it out of the box, and browser-side handling via LibRaw WebAssembly inherits the library's partial Quattro support.

EXIF fields and Sigma's property lists are embedded in the container, but MakerNote conventions differ enough from Bayer vendors that generic tools extract less; ExifTool provides the most complete parsing.

Convert X3F to another format