{"id":"image-x-sigma-x3f","mimeType":"image/x-sigma-x3f","name":"Sigma X3F RAW Image","shortName":"Sigma-X3F","category":"Photography \u0026 Raw Imaging","extensions":[".x3f"],"description":"The image/x-sigma-x3f MIME type represents the X3F RAW image format, primarily developed by Foveon, Inc. and utilized by Sigma Corporation for their digital cameras. Unlike traditional camera sensors that rely on a Bayer color filter mosaic (which captures only one color per pixel and interpolates the rest), Foveon X3 sensors feature three distinct layers of photodetectors stacked vertically to capture Red, Green, and Blue light at every single pixel location. Because an X3F file stores this unique, un-interpolated, full-color raw data, it avoids Bayer interpolation artifacts and produces incredibly sharp micro-contrast, though it requires highly specialized mathematical algorithms to demosaic and decode correctly.","seo":{"title":"image/x-sigma-x3f MIME Type | Developer Reference for Sigma X3F","description":"Complete reference for the image/x-sigma-x3f MIME type: Sigma X3F RAW format, Foveon X3 sensor technology, magic bytes, and raw image processing.","faqs":[{"question":"What is a Sigma X3F file?","answer":"An X3F file is a proprietary RAW image format used by Sigma digital cameras equipped with Foveon X3 sensors. It contains unprocessed, full-color sensor data without any JPEG compression."},{"question":"How is the X3F format different from other RAW files like CR2 or NEF?","answer":"Standard RAW files (like CR2 or NEF) usually come from sensors with a Bayer filter, where each pixel only captures red, green, or blue. X3F files come from Foveon sensors, which stack silicon layers to capture all three colors at every single pixel location. This fundamental hardware difference requires a completely different software architecture to decode."},{"question":"How do I open an X3F file?","answer":"Because of its unique stacked-sensor architecture, standard viewers cannot open X3F files. For the most accurate color reproduction, photographers use Sigma's official 'Sigma Photo Pro' software. Mainstream raw processors like Adobe Lightroom, Capture One, and RawTherapee also support most X3F variations."}]},"index":{"compression":["Uncompressed","Proprietary Lossless"],"browserSupport":{"score":1,"label":"None"},"commonUses":["Professional Digital Photography","Sigma / Foveon High-Acuity Imaging","Non-destructive RAW Post-Processing"]},"technical":{"magicBytes":{"hex":"46 4F 56 62","ascii":"FOVb"},"container":"Foveon Proprietary Header","compressionAlgorithm":["None","Foveon Proprietary Huffman-based"],"colorDepth":["12-bit (Per Channel)","14-bit (Per Channel)"],"transparency":false,"animation":false,"metadata":{"exif":true,"xmp":true,"iccProfile":true},"alphaChannel":false,"progressiveLoading":false,"hdrSupport":true},"history":{"developer":"Foveon, Inc. / Sigma Corporation","released":"2002","specification":"Proprietary (Heavily reverse-engineered by the LibRaw/dcraw community)"},"browserSupport":{"chrome":false,"chromeVersion":"None","firefox":false,"firefoxVersion":"None","safari":false,"safariVersion":"None","edge":false,"edgeVersion":"None","internetExplorer":false},"softwareSupport":[{"name":"Sigma Photo Pro","logo":""},{"name":"Adobe Lightroom Classic / CC","logo":""},{"name":"Capture One","logo":""},{"name":"RawTherapee","logo":""}],"conversion":{"convertTo":["dng","jpeg","tiff","png"],"convertFrom":[]},"developer":{"httpHeaders":[{"header":"Content-Type","value":"image/x-sigma-x3f"},{"header":"Content-Type","value":"image/x3f"}],"htmlAccept":"image/x-sigma-x3f, .x3f","fileDetection":["X3F files feature an unmistakable proprietary header distinct from TIFF-based RAW files.","Check the first 4 bytes for the ASCII string 'FOVb' (Hex: 46 4F 56 62), which stands for 'Foveon beginning'.","This magic header makes programmatic identification of X3F files highly reliable."]},"prosCons":{"pros":["Provides absolute per-pixel color accuracy without the interpolation artifacts or moiré patterns typical of Bayer-sensor RAW files","Unique 'FOVb' magic byte signature prevents accidental misidentification by standard file sniffers, unlike many TIFF-based raw formats","Incredible sharpness and detail resolution at the raw sensor level"],"cons":["Decoding is extremely computationally expensive and completely proprietary, meaning third-party software often struggles to match the color science of Sigma's own (famously slow) Photo Pro application","Massive file sizes because it records three complete RGB channels for every single spatial pixel coordinate","Zero support in web browsers or standard OS image viewers"]},"specifications":{"url":"https://www.libraw.org/","rfc":"","mimeAliases":["image/x3f"]},"developerSnippets":{"python":"import magic\n# Libmagic can easily detect the 'FOVb' Foveon header\nprint(magic.from_file('photo.x3f', mime=True)) # Outputs 'image/x-sigma-x3f' or 'image/x3f'","nodejs":"const fs = require('fs');\n// Manually detecting the 4-byte 'FOVb' magic signature\nconst buffer = Buffer.alloc(4);\nconst fd = fs.openSync('photo.x3f', 'r');\nfs.readSync(fd, buffer, 0, 4, 0);\nfs.closeSync(fd);\nconst isX3F = buffer[0] === 0x46 \u0026\u0026 buffer[1] === 0x4F \u0026\u0026 buffer[2] === 0x56 \u0026\u0026 buffer[3] === 0x62; // F, O, V, b\nconsole.log('Is Sigma X3F:', isX3F);","go":"import (\n    \"bytes\"\n    \"net/http\"\n)\n// Native Go HTTP detection might return application/octet-stream.\n// Check directly for the explicit 4-byte Foveon signature:\n// isX3F := bytes.HasPrefix(buf, []byte(\"FOVb\"))","php":"$mime = mime_content_type('photo.x3f');\necho $mime; // Standard PHP setups with updated magic definitions will return 'image/x-sigma-x3f'"},"relatedFormats":["dng","tiff"]}