Image MIME Reference
Sony-ARW
Sony Alpha Raw Image
image/x-sony-arw
VS
Windows Metafile
image/x-wmf
WMF
A complete technical comparison of Sony Alpha Raw Image and Windows Metafile — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | Sony-ARW | WMF |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | Yes | ✕ No |
| EXIF Metadata | Yes | ✕ No |
| ICC Color Profile | Yes | ✕ No |
Sony Alpha Raw Image
image/x-sony-arw
Extension
.arw
Container
TIFF-based (Proprietary)
Compression
Uncompressed / Lossless Compressed / Lossy Compressed
Algorithm
NoneSony Proprietary LosslessSony Proprietary Lossy
Color Depth
12-bit (Per Channel), 14-bit (Per Channel)
Developed by
Sony Corporation
Released
2006
Magic Bytes
49 49 2A 00
Windows Metafile
image/x-wmf
Extension
.wmf.emf
Container
Windows GDI Metafile Command Stream
Compression
Uncompressed (Command Stream)
Algorithm
None
Color Depth
Varies based on GDI rendering engine
Developed by
Microsoft Corporation
Released
1990
Magic Bytes
D7 CD C6 9A (Aldus Placeable Metafile Header) or 01 00 09 00 (Standard WMF Header)
Browser Support Comparison
| Browser | Sony-ARW | WMF |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ |
✓
|
Sony-ARW
Sony-ARW Strengths
- Retains absolute maximum sensor data, enabling massive shadow recovery and highlight protection compared to compressed in-camera JPEGs
- Embeds high-quality JPEG previews and robust metadata, allowing photographers to match in-camera color science (like Creative Looks) perfectly during raw processing
- Utilizes the standard TIFF container structure, ensuring broad compatibility with open-source decoding libraries (like LibRaw)
Limitations
- Proprietary format means it requires constant updates to raw processing engines every time Sony releases a new camera model
- Sony's historically controversial lossy compression algorithm (often called 'star eater' due to spatial filtering artifacts) was a drawback for astrophotography in older ARW versions, though largely resolved in newer models with uncompressed/lossless options
- Cannot be directly embedded into web pages or used in standard HTML/CSS contexts
WMF
WMF Strengths
- Infinitely scalable vector format that remains remarkably compact for simple geometric illustrations and charts
- Historically served as a seamless conduit for copying and pasting vector graphics between disparate Windows applications via the system clipboard
Limitations
- Notoriously plagued by historic security vulnerabilities, making raw WMF parsing a vector for exploits in legacy software
- Completely obsolete and unsupported in modern web environments (browsers cannot render them)
- Strictly tied to the Windows GDI architecture, making cross-platform rendering inconsistent across Linux and macOS
When to choose which format
Sony-ARW
Use Sony-ARW when…
- Professional Digital Photography
- Non-destructive Image Post-Processing
- High Dynamic Range (HDR) Imaging Archival
WMF
Use WMF when…
- Legacy Microsoft Office Clip Art and Icons
- Windows GDI Graphics Export
- Early Windows Desktop Publishing