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Image MIME Reference
CMU-Raster

CMU Window Manager Raster

image/x-cmu-raster
VS

Sony Alpha Raw Image

image/x-sony-arw
Sony-ARW

A complete technical comparison of CMU Window Manager Raster and Sony Alpha Raw Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature CMU-Raster Sony-ARW
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
CMU Window Manager Raster
image/x-cmu-raster
Extension
.ras
Container CMU Window Manager Bitmap
Compression Uncompressed
Algorithm
None
Color Depth 1-bit (Monochrome), 8-bit (Indexed/Grayscale)
Developed by Carnegie Mellon University (CMU)
Released 1980s
Magic Bytes
F1 00 40 BB
Full CMU-Raster reference →
Sony Alpha Raw Image
image/x-sony-arw
Extension
.arw
Container TIFF-based (Proprietary)
Compression Uncompressed / Lossless Compressed / Lossy Compressed
Algorithm
NoneSony Proprietary LosslessSony Proprietary Lossy
Color Depth 12-bit (Per Channel), 14-bit (Per Channel)
Developed by Sony Corporation
Released 2006
Magic Bytes
49 49 2A 00
Full Sony-ARW reference →

Browser Support Comparison

Browser CMU-Raster Sony-ARW
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
CMU-Raster

CMU-Raster Strengths

  • Incredibly simple, uncompressed binary structure that was easy for early, memory-constrained UNIX workstations to parse and render
Limitations
  • Completely obsolete and unsupported outside of niche historical command-line tools like Netpbm
  • The shared '.ras' file extension causes frequent file misidentification and system conflicts
  • Lacks all modern imaging features, including metadata, compression, and alpha channel transparency
Sony-ARW

Sony-ARW Strengths

  • Retains absolute maximum sensor data, enabling massive shadow recovery and highlight protection compared to compressed in-camera JPEGs
  • Embeds high-quality JPEG previews and robust metadata, allowing photographers to match in-camera color science (like Creative Looks) perfectly during raw processing
  • Utilizes the standard TIFF container structure, ensuring broad compatibility with open-source decoding libraries (like LibRaw)
Limitations
  • Proprietary format means it requires constant updates to raw processing engines every time Sony releases a new camera model
  • Sony's historically controversial lossy compression algorithm (often called 'star eater' due to spatial filtering artifacts) was a drawback for astrophotography in older ARW versions, though largely resolved in newer models with uncompressed/lossless options
  • Cannot be directly embedded into web pages or used in standard HTML/CSS contexts

When to choose which format

CMU-Raster
Use CMU-Raster when…
  • Historical UNIX / Andrew Project Archival
  • Legacy Academic Computing Research
Sony-ARW
Use Sony-ARW when…
  • Professional Digital Photography
  • Non-destructive Image Post-Processing
  • High Dynamic Range (HDR) Imaging Archival

More comparisons

CMU-Raster vs ACES → Sony-ARW vs ACES → CMU-Raster vs APNG → Sony-ARW vs APNG → CMU-Raster vs AVCI → Sony-ARW vs AVCI → CMU-Raster vs AVCS → Sony-ARW vs AVCS → CMU-Raster vs AVIF → Sony-ARW vs AVIF → All comparisons →
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