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Image MIME Reference
ACES

ACES Image Container File

image/aces
VS

FlashPix

image/vnd.fpx
FPX

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

Equal browser support

Feature Support

Feature ACES FPX
Transparency (Alpha) Yes Yes
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes ✕ No
EXIF Metadata ✕ No Yes
ICC Color Profile ✕ No Yes
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 →
FlashPix
image/vnd.fpx
Extension
.fpx
Container Microsoft OLE Structured Storage (COM)
Compression JPEG (Lossy) / Uncompressed / Single-color (Solid)
Algorithm
JPEGNone
Color Depth 8-bit (Grayscale/Indexed), 24-bit (RGB), 32-bit (CMYK/RGBA)
Developed by Eastman Kodak, Microsoft, Hewlett-Packard, Live Picture
Released 1996
Magic Bytes
D0 CF 11 E0 A1 B1 1A E1
Full FPX reference →

Browser Support Comparison

Browser ACES FPX
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
FPX

FPX Strengths

  • Allowed early, low-RAM computers to view and edit massive, high-resolution digital photos instantly by only loading the needed tiles and resolutions
  • Pioneered the multi-resolution pyramid and tiling concepts heavily used today in modern deep-zoom and web mapping applications (like Google Maps)
Limitations
  • Completely obsolete and unsupported by modern web browsers or operating systems
  • Uses the complex, proprietary Microsoft OLE container format, making it incredibly difficult to parse or extract data from without dedicated legacy libraries
  • Prone to being misidentified by MIME sniffers as an old Microsoft Office document

When to choose which format

ACES
Use ACES when…
  • Visual Effects (VFX)
  • Digital Intermediate (DI)
  • Color Grading
  • Archival
FPX
Use FPX when…
  • Legacy Digital Photography
  • Kodak Picture CDs (Historical)
  • Early High-Resolution Image Viewers

More comparisons

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