Image MIME Reference
G3-Fax
Group 3 Fax Image
image/g3fax
VS
Minolta Raw Image
image/x-minolta-mrw
Minolta-MRW
A complete technical comparison of Group 3 Fax Image and Minolta Raw Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | G3-Fax | Minolta-MRW |
|---|---|---|
| Transparency (Alpha) | ✕ No | ✕ No |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | ✕ No | Yes |
| EXIF Metadata | ✕ No | Yes |
| ICC Color Profile | ✕ No | Yes |
Group 3 Fax Image
image/g3fax
Extension
.g3
Container
Raw Bitstream
Compression
Lossless (CCITT Group 3)
Algorithm
CCITT Group 3 (Modified Huffman / READ)
Color Depth
1-bit (Monochrome)
Developed by
CCITT (now ITU-T) / IETF
Released
1980
Magic Bytes
None (Raw Bitstream)
Minolta Raw Image
image/x-minolta-mrw
Extension
.mrw
Container
Proprietary MRW Container
Compression
Uncompressed / Proprietary Lossless
Algorithm
NoneProprietary Lossless
Color Depth
12-bit (Per Channel)
Developed by
Minolta (later Konica Minolta)
Released
2001
Magic Bytes
00 4D 52 4D
Browser Support Comparison
| Browser | G3-Fax | Minolta-MRW |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
G3-Fax
G3-Fax Strengths
- Extremely efficient compression for 1-bit black-and-white text and line art
- Standardized via RFC 1494 for email and internet fax transmission
- Low bandwidth requirements
Limitations
- Raw format lacks metadata (such as image width and resolution), requiring out-of-band information to decode accurately
- Strictly limited to 1-bit monochrome imagery
- Zero native web browser support
Minolta-MRW
Minolta-MRW Strengths
- Retains full, unadulterated sensor data from early CCD digital cameras, allowing modern demosaicing algorithms to extract far superior image quality than what was possible when the cameras were released
- Possesses a very distinct, unambiguous magic header (\x00MRM), making programmatic identification completely foolproof
Limitations
- Completely obsolete proprietary format that has not seen a new camera release since 2006
- Cannot be natively viewed in web browsers or standard operating system image viewers without specialized decoders
- Relies entirely on open-source reverse engineering (like LibRaw) for continued modern software compatibility
When to choose which format
G3-Fax
Use G3-Fax when…
- Telefacsimile (Fax) Transmission
- Internet Fax (T.37)
- Document Archiving
- Telephony Systems
Minolta-MRW
Use Minolta-MRW when…
- Vintage Digital Photography (Konica Minolta DiMAGE / Maxxum)
- Raw Imaging Archival
- Historical Camera Sensor Research