MEF to G4 Converter

MEF to G4 — browser conversion tool

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Batch Processing

Upload multiple MEF files at once and convert them all to G4 in a single session — saves time on large photo sets.

Server-Side Power

Heavy MEF processing happens on Convertio servers, not your device. Get G4 results without slowing down your machine.

Browser-Based Tool

Run the entire MEF to G4 conversion in your web browser. No installations, no system requirements beyond internet access.

How to convert MEF to G4

1

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

2

Choose g4 or any other format you need as a result (more than 200 formats supported)

3

Let the file convert and you can download your g4 file right afterwards

About formats

MEF is the proprietary RAW image format used by Mamiya medium-format digital cameras, introduced with the Mamiya ZD in 2004 and continued through subsequent models including the DM series. MEF files capture the unprocessed output from Mamiya's large-area CCD sensors — typically 48x36mm or larger — at 16 bits per channel, preserving the full dynamic range and color depth of the medium-format sensor before any demosaicing, white balance, or tonal processing takes place. The format uses a TIFF-based container that stores the raw Bayer-pattern data alongside embedded JPEG previews and extensive EXIF metadata including Mamiya lens identification, shutter speed, aperture, and metering information. Mamiya (later reorganized as Mamiya Digital Imaging and eventually merged into Phase One's operations) has a legacy stretching back to 1940 in medium-format film photography, and the MEF format represents the digital continuation of that tradition. One advantage is the medium-format sensor's inherent imaging qualities: the larger sensor area captures more light per pixel, producing lower noise floors, smoother tonal gradations, and a shallower depth-of-field rendering that medium-format photographers value for portrait, fashion, and landscape work. RAW flexibility is another practical strength — MEF files processed in Adobe Lightroom, Capture One, or dcraw allow photographers to apply modern demosaicing and noise reduction algorithms to these sensors, often extracting noticeably better results than the camera's original processing offered.
Developer: Mamiya
Initial release: 2004
G4 is a monochrome image format based on the ITU-T Group 4 facsimile coding standard (Recommendation T.6), ratified by the CCITT in 1984 as an improvement over Group 3 for use on error-free digital networks like ISDN rather than analog telephone lines. G4 files contain 1-bit image data compressed using exclusively two-dimensional Modified Modified READ (MMR) coding, where each scanline is encoded as a set of differences (changing elements) relative to the line above it. By eliminating the one-dimensional coding fallback and the end-of-line synchronization markers required by Group 3, G4 achieves 20-50% better compression ratios on typical document pages while producing a simpler, more regular bitstream. The format is most commonly encountered as a compression method within TIFF files (TIFF compression tag 4), where it became the standard archival format for scanned documents in enterprise document management, government records, and legal imaging systems. G4 compression is specified at 200, 300, or 400 dpi depending on the scanning application, with 300 dpi being the most common for archival-quality document imaging. One advantage is exceptional compression efficiency for document content: G4's two-dimensional prediction exploits the strong vertical correlation in text and line art pages, typically compressing a 300 dpi letter-size page to 30-50 KB — roughly half the size of equivalent Group 3 encoding. The format's entrenchment in document management infrastructure is another strength — G4 TIFF is the mandated format for many government digital records systems, court filing systems, and corporate archives, supported by every enterprise imaging platform.
Developer: ITU-T (CCITT)
Initial release: 1984

Frequently Asked Questions

Why convert MEF to G4?

MEF files from Mamiya cameras store massive sensor data — converting to G4 lets you use that quality in any application.

What opens G4 files?

G4 files can be opened with IrfanView, XnView, ImageMagick, and document management systems.

Is there a cost for converting MEF to G4?

Convertio offers free conversions for standard use. Premium plans are available for users who need higher volume.

Is my data secure when converting MEF to G4?

Your privacy is protected — uploaded files are deleted right after processing, and results are purged within 24 hours.

What devices support this MEF to G4 converter?

The converter works on any device with a web browser — desktop, laptop, tablet, or smartphone, regardless of OS.