Camera RAW
What is a MOS file?
Updated Jul 2026
MOS is the RAW image format written by Leaf digital camera backs, the high-end sensor units used on medium format cameras in professional and studio photography. It stores the sensor data untouched, so nothing is thrown away and quality stays as high as the hardware allows. The tradeoff is that almost nothing outside professional photo software can open it.
- Extension
- .mos
- Type
- Camera RAW
- Typically
- Leaf backs
- Metadata
- Carries EXIF
Why MOS exists
Leaf built digital backs that attached to medium format camera bodies, giving studio and commercial photographers a much larger sensor than a standard camera. Those backs save their files as MOS, a RAW format specific to Leaf hardware.
Like other RAW formats, a MOS file is closer to raw sensor data than a finished picture. Nothing is compressed away, no color decisions have been baked in yet, and the file assumes you'll process it afterward in dedicated software to get the final image. That makes it lossless, but it also makes the file large and dependent on software that understands Leaf's particular RAW structure.
People run into MOS files when they're working with archives from a studio, inherited a photographer's backup drive, or need to bring older Leaf back captures into a current workflow. Most modern editing tools and every general image viewer draw a blank on it, so converting to TIFF or JPG is usually the first step before the images can be viewed, edited, or shared.
The trade-offs
Strengths
- Lossless, keeps the full detail the Leaf sensor captured
- Preserves maximum flexibility for later color and exposure work
- Retains shooting metadata alongside the image data
Watch-outs
- Only opens in software built to handle Leaf RAW files
- Large file sizes compared to processed formats
- Not viewable in standard photo viewers or on the web without converting
A note on privacy
MOS files carry embedded shooting metadata, including camera settings and sometimes location and timestamp details from the shoot. Uploading a batch of them to a web converter means that metadata, along with the actual image data, travels to and sits on someone else's server. Converting on your own machine keeps both the RAW files and everything attached to them local.
Questions
How do I open a MOS file?
You need software built to read Leaf RAW files, or a converter that supports the format. Standard photo viewers and most editors won't recognize it on their own.
Is MOS better than DNG?
Neither is strictly better. MOS is a manufacturer-specific RAW format, while DNG is a more widely supported open standard some tools convert RAW files into. DNG is easier to work with broadly; MOS keeps the original Leaf-specific data intact.
Why does my camera save files as MOS?
If you're shooting with a Leaf digital back, MOS is simply its native RAW output. It's not a setting you change, it's how that hardware writes its sensor data.
Can I convert MOS files without uploading them?
Yes. A desktop app like Morphjet converts MOS files on your own computer, so studio images and their metadata never leave your machine.
Morphjet opens and converts MOS and 1,800+ other formats, all on your own computer. Launching this July.