MOS to JFIF Converter
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Supports: MOS
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Need help?MOS to JFIF Converter
.mos is the raw capture format written by Leaf medium-format digital backs — the Aptus and Aptus-II line that mounted on Mamiya and Hasselblad bodies. It is not a picture yet: it holds the sensor's colour-filter-array readings in a TIFF-derived container along with the metadata a raw converter needs to interpret them, which is why a general-purpose viewer shows nothing even though the file looks TIFF-shaped from the outside.
.jfif is a JPEG. Not a relative of one — the same compressed image data in the same wrapper, under a different four characters after the dot. This page develops the raw and writes the result under that specific extension, which is what you want when an importer, an archive schema or a legacy piece of software asks for .jfif by name.
What Each Format Actually Is
| Property | .mos source |
.jfif output |
|---|---|---|
| Full name | Leaf Aptus raw capture | JPEG File Interchange Format |
| Origin | Leaf Imaging — a division of Scitex, later Kodak, finally a Phase One subsidiary | Published as JFIF 1.02 in 1992; formalised as ITU-T T.871 in May 2011 |
| Underlying structure | TIFF-derived container holding sensor data | JPEG marker segments — ITU-T T.81 compressed data plus density and colour conventions |
| Pixel state | Colour-filter-array mosaic, one channel per photosite | Fully demosaiced 8-bit sRGB |
| Bit depth | 16-bit sensor readout | 8 bits per channel |
| Transparency | None — a sensor has no alpha | None — JPEG has no alpha channel |
| Editing latitude | Full: white balance, exposure and tone are still adjustable | None: those decisions are baked in |
| What opens it | Capture One, Leaf Capture, LibRaw-based tools | Every browser and image editor ever written |
| Successor in the same family | Phase One .iiq, used by the later Leaf Credo backs |
n/a |
How to Convert MOS to JFIF
- Upload Your MOS File: Drag the
.mosonto the page or click "+ Add Files". A whole shoot can be queued and every frame converts with the same settings; medium-format raws are large, so the wait you notice is the upload rather than the conversion. - Pick a Quality Preset: Under Image Compression, Quality Preset opens on Very High (Recommended), which writes JPEG quality 95. The seven rungs map to fixed quality numbers, listed below.
- Or Set a Specific File Size Instead: Specific file size is the alternative mode, opening at 8 MB with an Auto Scale toggle. Leave Auto Scale on and the converter may reduce pixel dimensions as well as quality to reach your number; switch it off and it has to hit the target on compression alone.
- Set Image resolution and Convert: Image resolution opens on Keep original, preserving the back's full pixel count, with Resolution Percentage, Preset Resolutions, Width, Height and Width x Height available. Click Convert and save the
.jfif. Files upload over an encrypted connection, are developed and converted on our servers, and are deleted automatically after a few hours — no sign-up, no watermark.
The Quality Preset Ladder
Each rung is a fixed JPEG quality value handed to the encoder, so you can choose by number rather than by adjective:
| Quality Preset | JPEG quality | Where it fits |
|---|---|---|
| Highest | 100 | Print and archive copies; still lossy, and the returns above 95 are slight |
| Very High (opens here) | 95 | The general-purpose choice — hard to distinguish from the developed render |
| High | 90 | Client proofs and portfolio uploads at full pixel count |
| Medium | 80 | Web delivery where page weight matters more than pixel-peeping |
| Low | 70 | Contact sheets and quick review copies |
| Very Low | 60 | Thumbnails |
| Lowest | 50 | Placeholders; visible blocking in smooth gradients |
The thing to weigh against those numbers is the pixel count they multiply. A Leaf back's frame is tens of megapixels, and quality 95 across that many of them is a genuinely large JPEG. If size matters more than the last few percent of fidelity, drop Image resolution before you drop the preset — halving both dimensions removes three quarters of the pixels and costs far less visually than pushing the quality number down.
What Developing the Raw Bakes In
The .mos reaches our servers as sensor readings, and turning those into a picture is real work, not a container swap. The raw coder demosaics the colour-filter-array pattern so every pixel gets red, green and blue values; it applies the as-shot neutral the back recorded so greys read as grey; and it remaps the sensor's linear response through a standard tone curve before encoding to 8-bit sRGB.
That is a neutral, reasonable development — and it is worth being precise about what it is not. There is no HDR tone-mapping stage anywhere in the pipeline, so highlight rolloff comes from the standard curve rather than from a scene-referred operator. A frame you exposed deliberately to hold a bright sky may still clip where your own Capture One recipe would have pulled it back. It is also not your profile: Leaf's camera profiles and whatever recipe you have built live in your raw editor, not here. For colour-critical work, develop in Capture One and convert the export.
Standard shooting metadata does survive. We ran a JPEG carrying Make, Model, ISO, F Number and Exposure Time through the same encoder path this page uses and every field came back intact on the other side. What does not carry over is the raw-specific layer — the maker-note blocks and processing instructions that describe how to develop the sensor data. Once the file is developed there is nothing left for them to describe.
Frequently Asked Questions
Is a .jfif file different from a .jpg?
Not in any way that affects the bytes. JFIF is the interchange specification that defines how JPEG-compressed data is packaged — the marker segments, the pixel-density fields, the colour conventions a decoder expects — and .jpg files are JFIF files too. Written at the same quality from the same source, a .jfif and a .jpg are the same picture in the same wrapper. The only practical difference is that a few older applications filter their file pickers on .jpg alone and therefore never show your .jfif. Renaming fixes that completely, or JFIF to JPG does it without touching the filename by hand.
Why can I not choose between .jfif and .jpg on this page?
Because this page writes .jfif and only .jfif — the file-extension selector that appears on the general JPEG converter does not render here. That is the point of a dedicated JFIF route: you land on it precisely because something in your workflow names that extension. If you want the choice at conversion time, use MOS to JPG instead.
Which Leaf backs write .mos files?
Both generations of the Aptus line — the original Aptus backs and the later Aptus-II series, which run across a wide range of resolutions and reach 80 megapixels on the largest Aptus-II models. Leaf moved to Phase One's .iiq format for the Credo backs that followed, so if your files end in .iiq rather than .mos you are on a Credo and this is the wrong page. Some Leaf backs can also write .mos in a compressed variant as well as uncompressed, and not every raw engine reads both; if one file from a shoot fails while its neighbours succeed, that difference is the usual explanation.
How much quality am I losing?
Two separate losses, and it helps to keep them apart. The larger one is editing latitude: developing the raw bakes in white balance, exposure and tone, and the recovery headroom that justified shooting medium format simply is not present in an 8-bit JPEG. The smaller one is JPEG compression itself, which at the default quality 95 is not visible at normal viewing distances. Treat the .mos as the master and the .jfif as delivery — and if you want a delivery file that keeps 16-bit depth, MOS to TIFF is the better target.
Can the JFIF have a transparent background?
No, on both counts. JPEG has no alpha channel in any of its variants, and a raw sensor readout has no transparency to contribute in the first place — every photosite recorded light. If you need a cut-out for compositing, develop to a format that carries alpha with MOS to PNG and do the masking in an editor.
My frame is tens of megapixels and the JFIF is enormous. What should I change?
Resolution first, quality second. Under Image resolution pick a Preset Resolution such as 2160p or type explicit dimensions under Width x Height — that is where the bytes actually live. If you need to land on a specific number rather than a specific size, switch Image Compression to Specific file size, type the budget and leave Auto Scale on so the converter is allowed to reduce dimensions as well as compression to reach it. For an already-converted file, the image compressor takes it from there.
Why does my converted file look flatter than the preview in Capture One?
Because Capture One is showing you Leaf's camera profile plus every adjustment in your recipe, and this converter applies neither. What you get is a neutral standard development — demosaic, as-shot white balance, standard tone curve, sRGB encode. It is a faithful rendering of the sensor data and a poor imitation of your grade. When the look matters, do the work in your raw editor and convert the exported file rather than the raw.
One file from my shoot was rejected while the rest converted. Why?
The two usual causes are a compression variant the raw engine does not handle and a file that was never fully written. The first is fixable: open the frame in Leaf Capture or Capture One and re-save it uncompressed, or export a 16-bit TIFF and convert that with TIFF to JPG. The second is not — a card pulled mid-write or a backup that copied incompletely leaves a truncated .mos that no converter can reconstruct. Re-copy from the original card or another backup.
What happens to my raw files after the conversion?
They are uploaded over an encrypted connection, developed and converted on our servers, and both the uploads and the finished JFIFs are deleted automatically after a few hours. Nothing is shared or made public, there is no watermark and no account is required. The practical ceiling on a batch is upload size and connection speed rather than anything on our side, so a folder of medium-format raws is usually best sent in batches of a few dozen.