Convert MEF to JXL

Why Convert MEF to JXL?

Converting MEF to JXL addresses the growing concern of format obsolescence for Mamiya medium-format RAW files. Since Phase One acquired Mamiya in 2015, the MEF format has become a legacy artifact with no new cameras producing it and declining software support. Converting your processed Mamiya files to JXL — an ISO standard backed by the international JPEG committee — ensures that your medium-format photography remains accessible and manageable for decades to come.

Mamiya medium-format cameras produce files ranging from 40 to 120 MB per image. A professional shoot generating hundreds of frames creates enormous storage demands. JXL's efficient lossless compression typically reduces processed medium-format images by 60-80% compared to uncompressed TIFF, making it practical to maintain complete archives without excessive storage infrastructure. For a photographer with 50,000 career images, this can mean the difference between needing a multi-drive NAS and a single large SSD.

The quality of Mamiya's CCD sensors — particularly the Mamiya ZD and early Leaf Aptus backs — is legendary among medium-format photographers for their color accuracy and tonal rendering. JXL's lossless compression and full ICC profile support ensure that these distinctive characteristics are preserved perfectly in the converted files. The 16-bit processing pipeline feeds directly into JXL's high bit-depth support, maintaining the tonal precision that makes medium-format photography special.

For commercial photographers delivering retouched work to clients, JXL provides a practical alternative to enormous TIFF or PSD files. Clients can receive JXL files that open quickly thanks to progressive decoding, display at full medium-format resolution, and take up a fraction of the bandwidth during transfer. This improves the professional delivery experience while maintaining the quality that medium-format work demands.

Key Benefits of Converting MEF to JXL:

• Format Security: Move from legacy Mamiya format to ISO standard
• Storage Savings: 60-80% smaller than TIFF while maintaining quality
• Color Preservation: ICC profiles maintain Mamiya's renowned color rendering
• 16-bit Support: Full processing precision preserved in JXL
• Quick Client Preview: Progressive decode for instant access to large images
• Cross-Platform: No Mamiya-specific software needed to view
• Future-Proof: ISO 18181 standard guarantees long-term readability

Practical Examples

Example 1: Commercial Fashion Shoot Archive

Scenario: A fashion photographer has 8 years of editorial work shot on Mamiya 645DF with Leaf Aptus 75S backs (33 MP). They need to consolidate 25,000 processed images from expensive RAID storage into a manageable archive.

Source: editorial_ss2018_look12.mef (75 MB, 6726x8964px, 16-bit)
Processing: Capture One → color grade, skin retouch
Conversion: Processed MEF → JXL (lossless, 16-bit)
Result: editorial_ss2018_look12.jxl (18 MB, lossless)

Archive consolidation:
✓ 25,000 images: 1.8 TB processed → 450 GB JXL (75% reduction)
✓ From 4-bay RAID to single 1 TB SSD
✓ Every pixel preserved in lossless compression
✓ 16-bit color depth maintained for future reuse
✓ Annual storage cost savings: significant

Example 2: Gallery Exhibition Print Preparation

Scenario: An art photographer is preparing 40 large-format prints from Mamiya ZD captures for a gallery exhibition. The print shop needs high-resolution files, and the gallery wants digital versions for their online catalog.

Source: abstract_cityscape_09.mef (52 MB, 5344x4008px, 14-bit)
Processing: darktable → fine art B&W conversion, toning
Print file: Processed → JXL (lossless, 16-bit) = 12 MB
Web file: Processed → JXL (quality 90, effort 7) = 380 KB

Dual-output workflow:
✓ Lossless JXL for print production (12 MB vs 200 MB TIFF)
✓ Lossy JXL for gallery website (380 KB, visually perfect)
✓ 40 prints × 12 MB = 480 MB total (vs 8 GB as TIFF)
✓ Gallery website loads fast with progressive decode
✓ Single processing pipeline, two JXL quality levels

Example 3: Studio Product Photography Delivery

Scenario: A product photographer shot a luxury watch catalog on Mamiya DM40 (40 MP) with detailed macro shots. The advertising agency needs high-resolution files for print and web with fast download.

Source: rolex_daytona_detail_03.mef (88 MB, 7320x5484px, 16-bit)
Processing: Capture One → color match, focus stack merge
Conversion: Processed → JXL (quality 97, effort 9)
Result: rolex_daytona_detail_03.jxl (5.8 MB, near-lossless)

Client delivery advantages:
✓ 88 MB RAW → 5.8 MB JXL (93% smaller for transfer)
✓ Agency downloads 200 images in minutes, not hours
✓ Progressive decode shows instant preview for art director
✓ Quality indistinguishable from lossless at q97
✓ Zoom reveals watch mechanism details at full resolution

Frequently Asked Questions (FAQ)

Q: Which Mamiya cameras produce MEF files?

A: MEF files are produced by Mamiya's medium-format digital cameras and backs, including the Mamiya ZD (2004, 22 MP), Mamiya DM22/DM28/DM33/DM40/DM56 series, and various Leaf Aptus and Credo digital backs that were sold under the Mamiya/Leaf brand before Phase One's acquisition. After the acquisition, new backs use Phase One's IIQ format instead.

Q: Is MEF format at risk of becoming unsupported?

A: Yes. With Mamiya absorbed into Phase One and no new MEF-producing cameras being manufactured, support for the format depends on continued maintenance in open-source libraries like LibRaw. While LibRaw currently handles MEF well, the format's niche status means it could lose priority in future library updates. Converting to JXL eliminates this long-term risk.

Q: Will 16-bit color data be preserved in JXL?

A: Yes. JXL supports up to 32-bit float per channel, fully accommodating 14-16 bit processed output from Mamiya sensors. When using lossless JXL encoding with 16-bit input, every value is preserved exactly. This is critical for medium-format photography where the extended bit depth provides the smooth tonal gradations and highlight recovery that distinguish medium-format from smaller formats.

Q: How does MEF to JXL compare to MEF to TIFF for archival?

A: Both preserve the processed image at full quality in lossless mode. The difference is file size: JXL lossless is typically 60-80% smaller than TIFF LZW for the same image. A 200 MB 16-bit TIFF becomes 40-80 MB as lossless JXL. JXL also adds progressive decoding for fast previews, which TIFF lacks. For archival purposes, JXL is the superior choice — smaller, faster, and equally future-proof as an ISO standard.

Q: Can Capture One export directly to JXL?

A: As of early 2026, Capture One does not natively export to JXL. The typical workflow is to export from Capture One as 16-bit TIFF or PNG, then convert to JXL using this converter or command-line tools. As JXL adoption grows, Capture One and other professional RAW processors are expected to add native JXL export. Until then, the two-step workflow is straightforward and preserves full quality.

Q: How long does conversion take for a 40 MP MEF file?

A: RAW demosaicing of a 40 MP MEF file takes 5-15 seconds depending on hardware. JXL encoding at moderate effort (5-7) adds 5-20 seconds. Total conversion time is typically 10-35 seconds per image. For the highest compression (effort 9), encoding can take 1-3 minutes per image. For batch processing, effort level 5-7 provides an excellent compression-speed balance.

Q: Are the Mamiya CCD sensors' color characteristics preserved?

A: Yes. The distinctive color rendering of Mamiya CCD sensors (particularly valued for skin tones and color accuracy) is applied during the RAW processing stage through color matrices and profiles. Once processed, these color characteristics are embedded in the pixel data and ICC profile, which JXL preserves perfectly. The processed JXL output will display the same Mamiya color signature on any calibrated display.

Q: Should I use lossless or lossy JXL for commercial work?

A: Use lossless JXL for your master archive and print-ready files — these represent your highest-quality output and should never have compression artifacts. Use lossy JXL (quality 90-97) for client web proofs, portfolio galleries, and delivery packages where file size matters. At quality 95+, the difference from lossless is visually imperceptible on commercial photography, and the file size savings are substantial.