Image MIME Reference
G3-Fax
Group 3 Fax Image
image/g3fax
VS
Kodak Digital Camera Raw
image/x-kodak-dcr
Kodak-DCR
A complete technical comparison of Group 3 Fax Image and Kodak Digital Camera Raw — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | G3-Fax | Kodak-DCR |
|---|---|---|
| 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)
Kodak Digital Camera Raw
image/x-kodak-dcr
Extension
.dcr
Container
TIFF/EP
Compression
Uncompressed / Lossless JPEG
Algorithm
NoneLossless JPEG (ITU-T81)
Color Depth
12-bit (Per Channel)
Developed by
Eastman Kodak Company
Released
1998
Magic Bytes
49 49 2A 00 or 4D 4D 00 2A
Browser Support Comparison
| Browser | G3-Fax | Kodak-DCR |
|---|---|---|
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
Kodak-DCR
Kodak-DCR Strengths
- Preserves the full dynamic range and uncompressed raw sensor data captured by foundational professional digital cameras
- Utilizes the standard TIFF container structure, ensuring that open-source decoders like LibRaw can easily parse and interpret the files long after official vendor support has ended
Limitations
- Completely obsolete proprietary format tied to camera hardware that is no longer manufactured
- Shares the TIFF magic header, leading to widespread misidentification by automated MIME detection libraries
- Cannot be natively viewed in web browsers or standard operating system image viewers without specialized codecs
When to choose which format
G3-Fax
Use G3-Fax when…
- Telefacsimile (Fax) Transmission
- Internet Fax (T.37)
- Document Archiving
- Telephony Systems
Kodak-DCR
Use Kodak-DCR when…
- Vintage Professional Digital Photography (Kodak DCS series)
- Non-destructive Image Post-Processing
- Raw Imaging Archival