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Image MIME Reference
IEF

Image Exchange Format

image/ief
VS

Panasonic RAW Image

image/x-panasonic-raw
Panasonic-RAW-(RW2)

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

Equal browser support

Feature Support

Feature IEF Panasonic-RAW-(RW2)
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
Image Exchange Format
image/ief
Extension
.ief
Container TIFF Class B (TIFF-B)
Compression Lossless (MH, MR, MMR) / Uncompressed
Algorithm
MHMRMMRUncompressed
Color Depth 1-bit (Monochrome)
Developed by IETF Network Fax Working Group
Released 1992
Magic Bytes
49 49 2A 00 (Little-endian) / 4D 4D 00 2A (Big-endian)
Full IEF reference →
Panasonic RAW Image
image/x-panasonic-raw
Extension
.raw.rw2
Container TIFF-based (Proprietary)
Compression Uncompressed / Panasonic Proprietary Lossless
Algorithm
NoneProprietary Lossless
Color Depth 12-bit (Per Channel), 14-bit (Per Channel), 16-bit (Per Channel - High-res mode)
Developed by Panasonic Corporation
Released 2004
Magic Bytes
Older RAW: 49 49 2A 00 | Newer RW2: 49 49 55 00
Full Panasonic-RAW-(RW2) reference →

Browser Support Comparison

Browser IEF Panasonic-RAW-(RW2)
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
IEF

IEF Strengths

  • Provided a standard method for exchanging bi-level fax images during the early days of the Internet
  • Supported multi-page documents
  • Leveraged the highly resilient and well-documented TIFF container
Limitations
  • Completely obsolete and unsupported in modern computing environments
  • Strictly limited to 1-bit monochrome data, lacking color or grayscale capabilities
  • Magic bytes overlap completely with standard TIFF, making specific filetype detection difficult without parsing internal tags
Panasonic-RAW-(RW2)

Panasonic-RAW-(RW2) Strengths

  • Retains maximum sensor data, allowing significant recovery of highlights and shadows compared to in-camera JPEGs
  • Modern RW2 files embed proprietary lens correction profiles (distortion, vignetting, chromatic aberration) that raw converters can automatically apply
  • The unique 'IIU' signature on RW2 files makes programmatic identification extremely reliable compared to other TIFF-spoofing raw formats
Limitations
  • Proprietary format requires continuous updates to third-party processing engines whenever Panasonic releases a new Lumix camera
  • Produces very large file sizes, particularly when using Panasonic's High-Resolution multi-shot modes
  • Cannot be directly embedded into web pages or used in standard HTML/CSS contexts

When to choose which format

IEF
Use IEF when…
  • Legacy Fax Transmissions
  • Early Internet Gateways
  • Archival
Panasonic-RAW-(RW2)
Use Panasonic-RAW-(RW2) when…
  • Professional Digital Photography
  • Non-destructive Image Post-Processing
  • High Dynamic Range (HDR) Lumix Archival

More comparisons

IEF vs ACES → Panasonic-RAW-(RW2) vs ACES → IEF vs APNG → Panasonic-RAW-(RW2) vs APNG → IEF vs AVCI → Panasonic-RAW-(RW2) vs AVCI → IEF vs AVCS → Panasonic-RAW-(RW2) vs AVCS → IEF vs AVIF → Panasonic-RAW-(RW2) vs AVIF → All comparisons →
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