Camera RAW
What is an MEF file?
Updated Jul 2026
MEF is the raw image format used by Mamiya digital cameras, mostly medium format cameras aimed at professional photographers. It stores the unprocessed sensor data straight off the camera, so no detail is lost to compression. Most photo viewers and editors outside specialized raw software can't open it directly.
- Extension
- .mef
- Type
- Camera RAW
- Typically
- Mamiya cameras
- Metadata
- Carries EXIF
Why MEF exists
Mamiya is a camera maker known for medium format cameras, used in studio, fashion, and landscape photography where a larger sensor captures very fine detail. When a Mamiya digital camera saves a shot as raw, it stores that sensor data in the MEF format.
Because MEF is lossless, it keeps every bit of information the sensor captured, along with exposure settings and other shooting metadata from the moment the photo was taken. That makes it valuable for photographers who plan to make heavy edits later, like adjusting exposure or color balance, without losing quality. The tradeoff is size, medium format raw files run large.
Most people run into MEF files when moving photos off a Mamiya camera and into an editor or viewer that doesn't recognize the format. Since MEF is far less common than mainstream raw formats, opening or sharing it usually means converting it to something more universal like JPG or TIFF first.
The trade-offs
Strengths
- Captures full detail from a medium format sensor without compression loss
- Keeps camera settings and shooting data attached for editing later
- Suited to professional workflows that need maximum image quality
Watch-outs
- Very large file sizes compared to JPG or standard raw formats
- Not readable by most photo viewers or editors without conversion
- Limited software support outside professional raw workflows
A note on privacy
MEF files carry EXIF metadata, including camera settings and often the GPS location where the photo was taken. Uploading one to an online converter sends that photo and everything embedded in it to someone else's server. Converting it on your own computer keeps the image and its data on your machine.
Questions
How do I open a MEF file?
Specialized raw photo editors that support Mamiya cameras can open MEF directly. For a general photo viewer, you'll usually need to convert it to JPG, TIFF, or another common format first.
Is MEF better than JPG?
For image quality and editing flexibility, yes, MEF keeps everything the sensor captured. But JPG is far smaller and opens everywhere, so most people convert to JPG once their editing is done.
Why does my camera save photos as MEF?
Mamiya digital cameras save in MEF when shooting in raw mode, which preserves the full sensor data for later editing instead of compressing the image in-camera.
Can I convert MEF without uploading it?
Yes. A desktop app like Morphjet converts MEF files on your own computer, so the raw image and its metadata never leave your machine.
Morphjet opens and converts MEF and 1,800+ other formats, all on your own computer. Launching this July.