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Image MIME Reference
Epson-ERF

Epson Raw Format

image/x-epson-erf
VS

PWG Raster Format

image/pwg-raster
PWG-Raster

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

Equal browser support

Feature Support

Feature Epson-ERF PWG-Raster
Transparency (Alpha) ✕ No ✕ No
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile ✕ No ✕ No
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 →
PWG Raster Format
image/pwg-raster
Extension
.pwg.ras
Container CUPS Raster v2 Container
Compression PackBits (Run-Length Encoding)
Algorithm
PackBits (Apple RLE variant)
Color Depth 1-bit (Monochrome/K), 8-bit (Grayscale), 24-bit (sRGB / Adobe RGB), 32-bit (CMYK)
Developed by IEEE-ISTO Printer Working Group (PWG)
Released 2011
Magic Bytes
52 61 53 32
Full PWG-Raster reference →

Browser Support Comparison

Browser Epson-ERF PWG-Raster
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
PWG-Raster

PWG-Raster Strengths

  • The undisputed global standard for modern, driverless printing environments, eliminating the nightmare of installing manufacturer-specific print drivers
  • Extremely lightweight to decode on embedded hardware, requiring minimal RAM buffers on the printer side
  • Strict color space and resolution rules guarantee that the printed output will successfully process without syntax errors
Limitations
  • Generates massive file sizes and network payloads compared to vector-based formats like PDF or PostScript, as every page is fully rasterized at 300+ DPI before transmission
  • No support for native rendering in web browsers, image viewers, or graphic design software without specialized CUPS developer tools
  • Cannot store complex metadata, vector text, or layers

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
PWG-Raster
Use PWG-Raster when…
  • Driverless Network Printing (IPP Everywhere)
  • Apple AirPrint and Mopria Print Service Pipelines
  • CUPS (Common UNIX Printing System) Spooling

More comparisons

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