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Image MIME Reference
ACES

ACES Image Container File

image/aces
VS

Windows Metafile

image/x-wmf
WMF

A complete technical comparison of ACES Image Container File and Windows Metafile — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature ACES WMF
Transparency (Alpha) Yes Yes
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes ✕ No
EXIF Metadata ✕ No ✕ No
ICC Color Profile ✕ No ✕ No
ACES Image Container File
image/aces
Extension
.exr
Container OpenEXR (SMPTE ST 2065-4)
Compression Lossless / Uncompressed
Algorithm
PIZZIPRLEB44Uncompressed
Color Depth 16-bit (Half-float), 32-bit (Float)
Developed by Academy of Motion Picture Arts and Sciences (AMPAS) / SMPTE
Released 2013
Magic Bytes
76 2F 31 01
Full ACES reference →
Windows Metafile
image/x-wmf
Extension
.wmf.emf
Container Windows GDI Metafile Command Stream
Compression Uncompressed (Command Stream)
Algorithm
None
Color Depth Varies based on GDI rendering engine
Developed by Microsoft Corporation
Released 1990
Magic Bytes
D7 CD C6 9A (Aldus Placeable Metafile Header) or 01 00 09 00 (Standard WMF Header)
Full WMF reference →

Browser Support Comparison

Browser ACES WMF
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕
✓
ACES

ACES Strengths

  • Industry standard for high-end visual effects, compositing, and color grading
  • Supports 16-bit half-float data, accurately capturing immense dynamic range without clipping
  • Standardized by SMPTE (ST 2065-4) to guarantee universal color interoperability across different post-production facilities
Limitations
  • Considerably larger file sizes than conventional consumer image formats
  • Completely unsupported in web browsers and most standard desktop viewers
  • Requires specialized compositing or color grading software to interpret and view the scene-linear data correctly
WMF

WMF Strengths

  • Infinitely scalable vector format that remains remarkably compact for simple geometric illustrations and charts
  • Historically served as a seamless conduit for copying and pasting vector graphics between disparate Windows applications via the system clipboard
Limitations
  • Notoriously plagued by historic security vulnerabilities, making raw WMF parsing a vector for exploits in legacy software
  • Completely obsolete and unsupported in modern web environments (browsers cannot render them)
  • Strictly tied to the Windows GDI architecture, making cross-platform rendering inconsistent across Linux and macOS

When to choose which format

ACES
Use ACES when…
  • Visual Effects (VFX)
  • Digital Intermediate (DI)
  • Color Grading
  • Archival
WMF
Use WMF when…
  • Legacy Microsoft Office Clip Art and Icons
  • Windows GDI Graphics Export
  • Early Windows Desktop Publishing

More comparisons

ACES vs APNG → WMF vs APNG → ACES vs AVCI → WMF vs AVCI → ACES vs AVCS → WMF vs AVCS → ACES vs AVIF → WMF vs AVIF → All comparisons →
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