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Image MIME Reference
Epson-ERF

Epson Raw Format

image/x-epson-erf
VS

JPEG Network Graphics

image/x-jng
JNG

A complete technical comparison of Epson Raw Format and JPEG Network Graphics — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature Epson-ERF JNG
Transparency (Alpha) ✕ No Yes
Animation Support ✕ No ✕ No
Progressive Loading ✕ No Yes
HDR Support Yes ✕ No
EXIF Metadata Yes Yes
ICC Color Profile ✕ No Yes
Epson Raw Format
image/x-epson-erf
Extension
.erf
Container TIFF/EP
Compression Uncompressed / Lossless JPEG (ITU-T81)
Algorithm
NoneLossless JPEG
Color Depth 12-bit (Per Channel)
Developed by Seiko Epson Corporation
Released 2004
Magic Bytes
49 49 2A 00 or 4D 4D 00 2A
Full Epson-ERF reference →
JPEG Network Graphics
image/x-jng
Extension
.jng
Container PNG-style Chunk Structure (JHDR, JDAT, IDAT, IEND)
Compression Lossy (JPEG/DCT for color) / Lossless (Deflate for alpha mask)
Algorithm
JPEG (Discrete Cosine Transform)Deflate (LZ77)
Color Depth 8-bit, 12-bit, 24-bit (RGB), 32-bit (RGBA)
Developed by MNG Development Group (Glenn Randers-Pehrson et al.)
Released 2001
Magic Bytes
8B 4A 4E 47 0D 0A 1A 0A
Full JNG reference →

Browser Support Comparison

Browser Epson-ERF JNG
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
Epson-ERF

Epson-ERF Strengths

  • Preserves original raw sensor data, allowing extreme recovery of highlights and shadows compared to in-camera JPEGs
  • Utilizes the standard TIFF container structure, making it relatively easy for open-source software (like dcraw and LibRaw) to parse and decode
Limitations
  • Completely obsolete proprietary format tied to a defunct line of digital cameras
  • Requires parsing EXIF metadata to differentiate it from standard TIFF files programmatically
  • Cannot be natively viewed in web browsers or standard operating system image viewers without specialized codecs
JNG

JNG Strengths

  • Solved a massive technical hurdle in the early 2000s by combining high-compression lossy photographic data with crisp, 8-bit alpha transparency
  • Utilized the highly robust, extensible chunk-based architecture of the PNG format
  • Provided an excellent, bandwidth-saving alternative to massive 32-bit transparent PNGs for web design
Limitations
  • Failed to achieve critical mass; browser vendors largely abandoned the MNG/JNG standard due to implementation complexity
  • Completely obsolete today, having been superseded by natively supported, superior formats like WebP, AVIF, and HEIC
  • Decoding requires a hybrid engine that can parse PNG chunks while simultaneously decoding a JPEG stream and a Deflate stream, complicating software support

When to choose which format

Epson-ERF
Use Epson-ERF when…
  • Vintage Digital Photography (Epson R-D1)
  • Non-destructive Image Post-Processing
  • Raw Imaging Archival
JNG
Use JNG when…
  • Embedded frames in MNG animations
  • Historical web graphics requiring lossy compression with transparency

More comparisons

Epson-ERF vs ACES → JNG vs ACES → Epson-ERF vs APNG → JNG vs APNG → Epson-ERF vs AVCI → JNG vs AVCI → Epson-ERF vs AVCS → JNG vs AVCS → Epson-ERF vs AVIF → JNG vs AVIF → All comparisons →
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