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Image MIME Reference
Sigma-X3F

Sigma X3F RAW Image

image/x-sigma-x3f
VS

Valve Texture Format

image/vnd.valve.source.texture
VTF

A complete technical comparison of Sigma X3F RAW Image and Valve Texture Format — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature Sigma-X3F VTF
Transparency (Alpha) ✕ No Yes
Animation Support ✕ No Yes
Progressive Loading ✕ No ✕ No
HDR Support Yes Yes
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
Sigma X3F RAW Image
image/x-sigma-x3f
Extension
.x3f
Container Foveon Proprietary Header
Compression Uncompressed / Proprietary Lossless
Algorithm
NoneFoveon Proprietary Huffman-based
Color Depth 12-bit (Per Channel), 14-bit (Per Channel)
Developed by Foveon, Inc. / Sigma Corporation
Released 2002
Magic Bytes
46 4F 56 62
Full Sigma-X3F reference →
Valve Texture Format
image/vnd.valve.source.texture
Extension
.vtf
Container Valve Texture Format Header
Compression DXTC (DXT1, DXT3, DXT5) / Uncompressed (BGRA8888, RGB888, etc.)
Algorithm
DXT1-DXT5None
Color Depth 8-bit, 24-bit (RGB), 32-bit (RGBA), 16-bit Floating Point (HDR)
Developed by Valve Corporation
Released 2004
Magic Bytes
56 54 46 00
Full VTF reference →

Browser Support Comparison

Browser Sigma-X3F VTF
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
Sigma-X3F

Sigma-X3F Strengths

  • 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
Limitations
  • 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
VTF

VTF Strengths

  • Extremely fast loading within the Source Engine because the block-compressed data goes directly into the GPU's VRAM without CPU decompression overhead
  • Bundles mipmaps, volumetric slices, cubemap faces, and animation frames entirely within a single file
  • Openly documented by the Valve Developer Community, leading to a massive ecosystem of third-party modding tools
Limitations
  • Strictly tied to the Source Engine ecosystem; entirely useless in standard web or print contexts
  • No native support in standard image editors without hunting down and installing specialized plugins
  • Block compression algorithms (DXT) are lossy and can cause visible artifacting, especially on normal maps or smooth gradients

When to choose which format

Sigma-X3F
Use Sigma-X3F when…
  • Professional Digital Photography
  • Sigma / Foveon High-Acuity Imaging
  • Non-destructive RAW Post-Processing
VTF
Use VTF when…
  • Source Engine Game Textures
  • Custom Maps and Modding (Garry's Mod, CS:GO)
  • Animated In-Game Decals and Sprays
  • Environment Cubemaps (Skyboxes)

More comparisons

Sigma-X3F vs ACES → VTF vs ACES → Sigma-X3F vs APNG → VTF vs APNG → Sigma-X3F vs AVCI → VTF vs AVCI → Sigma-X3F vs AVCS → VTF vs AVCS → Sigma-X3F vs AVIF → VTF vs AVIF → All comparisons →
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