Image MIME Reference
HEIC-Sequence
HEVC Image Sequence (HEIF Container)
image/heic-sequence
VS
Pentax Electronic File
image/x-pentax-pef
Pentax-PEF
A complete technical comparison of HEVC Image Sequence (HEIF Container) and Pentax Electronic File — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
HEIC-Sequence wins on browser support
Feature Support
| Feature | HEIC-Sequence | Pentax-PEF |
|---|---|---|
| Transparency (Alpha) | Yes | ✕ No |
| Animation Support | Yes | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | Yes | Yes |
| EXIF Metadata | Yes | Yes |
| ICC Color Profile | Yes | Yes |
HEVC Image Sequence (HEIF Container)
image/heic-sequence
Extension
.heics.heic
Container
HEIF / ISOBMFF (ISO/IEC 14496-12)
Compression
Lossy / Lossless
Algorithm
HEVC (H.265)
Color Depth
8-bit, 10-bit, 12-bit, 16-bit
Developed by
Moving Picture Experts Group (MPEG) / Apple
Released
2017
Magic Bytes
XX XX XX XX 66 74 79 70 68 65 76 63
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)
Browser Support Comparison
| Browser | HEIC-Sequence | Pentax-PEF |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✓ 11+
|
✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
HEIC-Sequence
HEIC-Sequence Strengths
- Incredibly efficient storage for bursts and short animations compared to GIF or motion JPEG
- Supports 16-bit color, HDR, and alpha channel transparency across all frames
- Shares frame data blocks, meaning the base image and animation data are heavily optimized for space
Limitations
- Zero support in web browsers outside the Apple ecosystem (Chrome, Firefox, Edge do not support it)
- Heavily encumbered by HEVC patent pools, hindering open-source adoption
- Complex container structure makes parsing and decoding difficult without specialized libraries
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
When to choose which format
HEIC-Sequence
Use HEIC-Sequence when…
- Apple Live Photos
- Burst Photography
- High-Quality Animations
- Cinemagraphs
Pentax-PEF
Use Pentax-PEF when…
- Professional Digital Photography
- Non-destructive Image Post-Processing
- Pentax Camera Archival