Image MIME Reference
Pentax-PEF
Pentax Electronic File
image/x-pentax-pef
VS
SealedMedia SoftSeal JPEG
image/vnd.sealedmedia.softseal.jpg
SoftSeal-JPEG
A complete technical comparison of Pentax Electronic File and SealedMedia SoftSeal JPEG — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | Pentax-PEF | SoftSeal-JPEG |
|---|---|---|
| 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 |
Pentax Electronic File
image/x-pentax-pef
Extension
.pef
Container
TIFF-based (Proprietary)
Compression
Uncompressed / Proprietary Lossless
Algorithm
NonePentax Proprietary Lossless
Color Depth
12-bit (Per Channel), 14-bit (Per Channel)
Developed by
Pentax (now Ricoh Imaging Company, Ltd.)
Released
2003
Magic Bytes
49 49 2A 00 (Little-endian) or 4D 4D 00 2A (Big-endian)
SealedMedia SoftSeal JPEG
image/vnd.sealedmedia.softseal.jpg
Extension
.sjpg.sealed-jpg.sealed-jpeg
Container
SealedMedia SoftSeal Wrapper
Compression
Encrypted Payload (DCT)
Algorithm
AES EncryptionDiscrete Cosine Transform (Internal JPEG payload)
Color Depth
Encrypted Payload (Historically 24-bit RGB)
Developed by
SealedMedia (Acquired by Oracle Corporation)
Released
Late 1990s
Magic Bytes
Unknown (Proprietary SealedMedia Container)
Browser Support Comparison
| Browser | Pentax-PEF | SoftSeal-JPEG |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
Pentax-PEF
Pentax-PEF Strengths
- Retains absolute maximum sensor data, enabling massive shadow recovery and highlight protection compared to compressed in-camera JPEGs
- White balance and sharpening are saved as metadata instructions rather than 'baked in', meaning they can be perfectly adjusted in post-production
- Utilizes the standard TIFF container structure, making it relatively straightforward for open-source software like LibRaw to parse
Limitations
- Proprietary format requires continuous updates to third-party processing software whenever Pentax releases a new camera model (unlike the open DNG format)
- Produces very large file sizes compared to standard web formats
- Cannot be directly embedded into web pages or used in standard HTML/CSS contexts
SoftSeal-JPEG
SoftSeal-JPEG Strengths
- Offered persistent document security; if a sensitive photo was emailed outside the company, it remained encrypted and unviewable without server authentication
- Administrators possessed the ability to remotely revoke viewing rights to a specific image globally at any time
Limitations
- Completely proprietary and relies on a central authentication server; if the server goes offline or the product is deprecated, the image is permanently inaccessible
- Zero support in modern operating systems, web browsers, or standard image editing suites without heavy enterprise client installations
- Oracle effectively discontinued the IRM product line, stranding many legacy sealed documents
When to choose which format
Pentax-PEF
Use Pentax-PEF when…
- Professional Digital Photography
- Non-destructive Image Post-Processing
- Pentax Camera Archival
SoftSeal-JPEG
Use SoftSeal-JPEG when…
- Enterprise Information Rights Management (IRM)
- Secure Distribution of Sensitive Photography
- Revocable Corporate Document Access