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Image MIME Reference
Pentax-PEF

Pentax Electronic File

image/x-pentax-pef
VS

Silicon Graphics Image

image/x-rgb
SGI-RGB

A complete technical comparison of Pentax Electronic File and Silicon Graphics Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature Pentax-PEF SGI-RGB
Transparency (Alpha) ✕ No Yes
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
Pentax Electronic File
image/x-pentax-pef
Extension
.pef
Container TIFF-based (Proprietary)
Compression Uncompressed / Proprietary Lossless
Algorithm
NonePentax Proprietary Lossless
Color Depth 12-bit (Per Channel), 14-bit (Per Channel)
Developed by Pentax (now Ricoh Imaging Company, Ltd.)
Released 2003
Magic Bytes
49 49 2A 00 (Little-endian) or 4D 4D 00 2A (Big-endian)
Full Pentax-PEF reference →
Silicon Graphics Image
image/x-rgb
Extension
.rgb.sgi.rgba.bw.int.inta
Container SGI Image Header (512 bytes)
Compression Uncompressed / Run-Length Encoding (RLE)
Algorithm
NoneScanline RLE
Color Depth 8-bit (Per Channel), 16-bit (Per Channel)
Developed by Silicon Graphics, Inc. (Paul Haeberli)
Released 1988
Magic Bytes
01 DA
Full SGI-RGB reference →

Browser Support Comparison

Browser Pentax-PEF SGI-RGB
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
Pentax-PEF

Pentax-PEF Strengths

  • Retains absolute maximum sensor data, enabling massive shadow recovery and highlight protection compared to compressed in-camera JPEGs
  • White balance and sharpening are saved as metadata instructions rather than 'baked in', meaning they can be perfectly adjusted in post-production
  • Utilizes the standard TIFF container structure, making it relatively straightforward for open-source software like LibRaw to parse
Limitations
  • Proprietary format requires continuous updates to third-party processing software whenever Pentax releases a new camera model (unlike the open DNG format)
  • Produces very large file sizes compared to standard web formats
  • Cannot be directly embedded into web pages or used in standard HTML/CSS contexts
SGI-RGB

SGI-RGB Strengths

  • Supports 16-bit precision per channel and an embedded alpha channel, making it ideal for the demanding compositing workflows of 1990s cinema VFX
  • The scanline-based RLE compression was exceptionally fast to decode on classic MIPS-based SGI workstations
  • Features a straightforward 512-byte header, making it relatively easy to parse and write custom decoders in C or Python
Limitations
  • Completely obsolete and unsupported in modern web environments
  • Replaced entirely by TIFF, OpenEXR, and PNG in modern visual effects and 3D rendering pipelines
  • Lacks support for modern color management via ICC profiles or advanced EXIF metadata

When to choose which format

Pentax-PEF
Use Pentax-PEF when…
  • Professional Digital Photography
  • Non-destructive Image Post-Processing
  • Pentax Camera Archival
SGI-RGB
Use SGI-RGB when…
  • Legacy 3D Animation and VFX Textures
  • Silicon Graphics IRIX Workstation Archival
  • 1990s Medical Imaging

More comparisons

Pentax-PEF vs ACES → SGI-RGB vs ACES → Pentax-PEF vs APNG → SGI-RGB vs APNG → Pentax-PEF vs AVCI → SGI-RGB vs AVCI → Pentax-PEF vs AVCS → SGI-RGB vs AVCS → Pentax-PEF vs AVIF → SGI-RGB vs AVIF → All comparisons →
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