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Image MIME Reference
Nikon-NEF

Nikon Electronic Format

image/x-nikon-nef
VS

Progressive JPEG (Legacy IE Alias)

image/pjpeg
PJPEG

A complete technical comparison of Nikon Electronic Format and Progressive JPEG (Legacy IE Alias) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

PJPEG wins on browser support

Feature Support

Feature Nikon-NEF PJPEG
Transparency (Alpha) ✕ No ✕ No
Animation Support ✕ No ✕ No
Progressive Loading ✕ No Yes
HDR Support Yes ✕ No
EXIF Metadata Yes Yes
ICC Color Profile Yes Yes
Nikon Electronic Format
image/x-nikon-nef
Extension
.nef
Container TIFF
Compression Uncompressed / Lossless Compressed / Lossy Compressed (High Efficiency)
Algorithm
NoneNikon Proprietary LosslessNikon High Efficiency Lossy
Color Depth 12-bit (Per Channel), 14-bit (Per Channel)
Developed by Nikon Corporation
Released 1999
Magic Bytes
49 49 2A 00 or 4D 4D 00 2A
Full Nikon-NEF reference →
Progressive JPEG (Legacy IE Alias)
image/pjpeg
Extension
.jpeg.jpg.pjpeg.pjp.jfif
Container JPEG (ISO/IEC 10918-1)
Compression Lossy (DCT)
Algorithm
Discrete Cosine Transform (DCT)
Color Depth 8-bit, 12-bit
Developed by Joint Photographic Experts Group / Microsoft (Alias)
Released 1992
Magic Bytes
FF D8 FF E0 (JFIF) / FF D8 FF E1 (Exif)
Full PJPEG reference →

Browser Support Comparison

Browser Nikon-NEF PJPEG
Chrome Chrome
✕
✓ All
Firefox Firefox
✕
✓ All
Safari Safari
✕
✓ All
Edge Edge
✕
✓ All
IE IE (Legacy)
✕
✓
Nikon-NEF

Nikon-NEF Strengths

  • Retains maximum sensor data, allowing extreme recovery of highlights and shadows that would be permanently lost in a JPEG
  • White balance, sharpening, and color profiling are saved as metadata instructions rather than 'baked in', meaning they can be completely altered in post-production without degrading the image
  • Embeds a high-quality JPEG preview inside the raw file for rapid culling and viewing
Limitations
  • Proprietary format means it requires constant updates to raw processing engines every time Nikon releases a new camera model
  • Produces very large file sizes (often 20MB to 50MB+ per image depending on sensor resolution and bit-depth)
  • Cannot be directly embedded into web pages or used in standard HTML/CSS contexts
PJPEG

PJPEG Strengths

  • Progressive JPEGs (which this MIME type attempted to describe) provide excellent perceived loading speeds on slow connections by rendering a low-resolution preview first
  • Files sent with this MIME type are fully backwards compatible with any standard JPEG decoder
Limitations
  • It is a non-standard MIME type that violates IANA specifications
  • Causes strict file upload validation scripts to fail if not explicitly whitelisted or mapped
  • Creates unnecessary confusion, as the official image/jpeg MIME type already fully encompasses progressive encoding

When to choose which format

Nikon-NEF
Use Nikon-NEF when…
  • Professional Digital Photography
  • Non-destructive Image Post-Processing
  • High Dynamic Range (HDR) Imaging Archival
PJPEG
Use PJPEG when…
  • Legacy Internet Explorer File Uploads
  • Progressive Image Rendering (Historical context)

More comparisons

Nikon-NEF vs ACES → PJPEG vs ACES → Nikon-NEF vs APNG → PJPEG vs APNG → Nikon-NEF vs AVCI → PJPEG vs AVCI → Nikon-NEF vs AVCS → PJPEG vs AVCS → Nikon-NEF vs AVIF → PJPEG vs AVIF → All comparisons →
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