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Image MIME Reference
Nikon-NEF

Nikon Electronic Format

image/x-nikon-nef
VS

T.38 Fax over IP (FoIP)

image/t38
T.38

A complete technical comparison of Nikon Electronic Format and T.38 Fax over IP (FoIP) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature Nikon-NEF T.38
Transparency (Alpha) ✕ No ✕ No
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
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 →
T.38 Fax over IP (FoIP)
image/t38
Extension
.t38
Container UDPTL or TCP (Network Transport)
Compression Lossless (MH, MR, MMR / T.4, T.6)
Algorithm
MH (Modified Huffman)MR (Modified Read)MMR (Modified Modified Read)
Color Depth 1-bit (Monochrome B&W)
Developed by ITU-T (International Telecommunication Union)
Released 1998
Magic Bytes
None (Network Stream)
Full T.38 reference →

Browser Support Comparison

Browser Nikon-NEF T.38
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
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
T.38

T.38 Strengths

  • Designed specifically to overcome the timing and packet-loss issues that plague traditional fax over standard VoIP audio codecs (like G.711)
  • Reduces bandwidth requirements by transmitting fax protocol data rather than uncompressed audio tones
  • Universally supported by enterprise SIP trunks and Session Border Controllers (SBCs) for FoIP
Limitations
  • Not an actual image file format, causing confusion due to its 'image/' MIME classification
  • Extremely complex to implement correctly over lossy UDP networks (relies on UDPTL redundancy mechanisms)
  • Zero support in web browsers or standard image viewing software

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
T.38
Use T.38 when…
  • Fax over IP (FoIP) Transmissions
  • SIP/SDP Media Negotiation
  • VoIP Gateways and PBX Systems
  • Enterprise Fax Servers

More comparisons

Nikon-NEF vs ACES → T.38 vs ACES → Nikon-NEF vs APNG → T.38 vs APNG → Nikon-NEF vs AVCI → T.38 vs AVCI → Nikon-NEF vs AVCS → T.38 vs AVCS → Nikon-NEF vs AVIF → T.38 vs AVIF → All comparisons →
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