What is an X3F file?

X3F is Sigma's RAW format, used exclusively with Foveon X3 sensor cameras including the SD9, SD10, SD14, SD15, SD1 / SD1 Merrill, DP1/DP2/DP3 Merrill compacts, the dp Quattro series (dp0/dp1/dp2/dp3 Quattro), and the sd Quattro and sd Quattro H. The Foveon sensor stacks red, green, and blue photosites vertically (unlike Bayer-pattern sensors which mosaic them horizontally), producing files with unusual color fidelity but heavy noise above ISO 400. Converting X3F to HEIC gives Foveon shooters a developed derivative that keeps 10-bit color depth - a real advantage for the smooth tonal gradients Foveon is famous for - at roughly half the size of an equivalent JPG.

Sigma Photo Pro (free from sigma-global.com) is the only software that fully processes X3F, because Foveon processing is a per-layer color separation Sigma developed in-house rather than true demosaicing. SPP cannot export HEIC directly - it exports 16-bit TIFF or JPG - so the highest-fidelity route is SPP to 16-bit TIFF, then TIFF to HEIC. Uploading the X3F straight to heic.now uses a LibRaw-based decode that is faster but renders a softer, more Bayer-like interpretation than the SPP signature look, which is fine for proofing and archives.

Landscape and architecture photographers who value Foveon's near-medium-format sharpness convert X3F to HEIC for iPad portfolio review, iCloud photo libraries, and long-term archives where storage matters. A dp0 Quattro X3F runs around 50MB; a 10-bit HEIC derivative lands around 4-8MB while preserving the tonal depth that an 8-bit JPG would flatten. For gallery submissions and print labs that require universal formats, derive a JPG from the HEIC with HEIC to JPG at the final step.

Reasons to convert X3F to HEIC usually come down to compatibility, file-size, or specific feature requirements. Common situations:

• An app or platform only accepts HEIC uploads.
• You need a feature unique to HEIC (e.g. transparency, vector scaling, animation, multi-page pages, etc.) that X3F doesn't provide.
• You're optimising file size — modern formats often produce smaller files than the older format you started with.
• You need a single archival format across a project so files behave consistently in the same viewer.

1. Open the X3F → HEIC tool on heic.now.
2. Drag your X3F file onto the drop zone, or click Select files. You can drop a whole folder of files at once.
3. The output is fixed to HEIC. If the format supports extra options (page size, transparency background, quality, EXIF stripping), tweak them in the right-hand panel.
4. Click Convert. The job runs on our server and finishes in a few seconds for typical photos.
5. Download the result. Files stay in storage for 24 hours and are then permanently deleted.

The entire flow is free for the first 10 jobs per day with no signup required. A free account doubles that quota; a premium plan removes the limit entirely.

• Use Sigma Photo Pro for processing when the Foveon signature look matters - export 16-bit TIFF from SPP, then convert TIFF to HEIC to keep 10-bit tonal depth.
• Stay below ISO 400 on Foveon - chroma noise above ISO 800 becomes uncorrectable; noisy X3F files are better converted to monochrome before HEIC archiving.
• Apply SPP's X3 Fill Light at +0.3 to +0.7 to recover Foveon's notoriously dark shadows before converting - HEIC's 10-bit depth preserves the recovered shadow detail cleanly.
• Keep the X3F originals - HEIC is a developed derivative, not a RAW replacement; the Foveon layer data cannot be reconstructed from any converted file.
• Check the receiving end before sharing HEIC - print labs, galleries, and most submission portals still expect JPG or TIFF, so convert the HEIC on the way out when needed.