Image MIME Reference
Sigma-X3F
Sigma X3F RAW Image
image/x-sigma-x3f
VS
Sony SRF Raw Image
image/x-sony-srf
Sony-SRF
A complete technical comparison of Sigma X3F RAW Image and Sony SRF Raw Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | Sigma-X3F | Sony-SRF |
|---|---|---|
| Transparency (Alpha) | ✕ No | ✕ No |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | Yes | Yes |
| EXIF Metadata | Yes | Yes |
| ICC Color Profile | Yes | Yes |
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
Sony SRF Raw Image
image/x-sony-srf
Extension
.srf
Container
TIFF-based (Proprietary)
Compression
Uncompressed
Algorithm
None
Color Depth
12-bit (Per Channel)
Developed by
Sony Corporation
Released
2003
Magic Bytes
49 49 2A 00
Browser Support Comparison
| Browser | Sigma-X3F | Sony-SRF |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
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
Sony-SRF
Sony-SRF Strengths
- Retains perfectly raw, unprocessed sensor data from legacy early-2000s cameras, allowing modern raw processors to extract much better dynamic range and color than the camera's original internal JPEG engine could
- Utilizes a standard TIFF container structure, ensuring broad compatibility with community-maintained open-source decoding libraries like LibRaw
Limitations
- Completely obsolete format that has long been abandoned in favor of ARW
- MIME detection via magic bytes is unreliable due to TIFF header spoofing, requiring deeper EXIF inspection for accurate routing
- Cannot be natively viewed in web browsers or standard operating system image viewers without specialized decoders
When to choose which format
Sigma-X3F
Use Sigma-X3F when…
- Professional Digital Photography
- Sigma / Foveon High-Acuity Imaging
- Non-destructive RAW Post-Processing
Sony-SRF
Use Sony-SRF when…
- Legacy Sony Cyber-shot Photography
- Non-destructive Image Post-Processing
- Early 2000s Raw Imaging Archival