MOS to AVIF Converter

Convert MOS to AVIF Online

A .mos file is the unprocessed RAW capture from a Leaf Aptus medium-format digital back — a large, high-bit-depth sensor negative that won't open in a browser or load on a web page. Converting it to AVIF renders that RAW into a finished still and encodes it with the AV1 codec, turning a decade-old studio frame into a small, modern web image that almost any current browser can display. Because a MOS is a clean, lossless source, it produces noticeably better AVIF output than re-compressing an existing JPEG would.

How to Convert MOS to AVIF

1. Upload Your MOS File: Drag and drop your Leaf .mos file onto the page or click "+ Add Files" to browse. You can queue several Aptus or Aptus-II captures at once, though each medium-format RAW can run from tens to over a hundred megabytes.
2. Pick a Quality Preset: Open Advanced Options and set the "Quality Preset" — "Very High (Recommended)" is the default and keeps fine studio detail; step down to "High" or "Medium" for a smaller file.
3. Target a File Size or Resolution (Optional): Switch to "Target file size (%)" or "Specific file size" to hit an exact web budget, or use "Image resolution" to downscale from the back's full pixel count to a preset like 1080p for faster page loads.
4. Convert and Download: Click "Convert" and download your AVIF. No sign-up, no watermark.

AVIF vs JPEG for a Rendered MOS

Frequently Asked Questions

Do I lose the RAW editing latitude when I convert MOS to AVIF?

Yes. A MOS stores high-bit-depth linear sensor data, which is why you can recover highlights and reset white balance long after the shot. To make an AVIF, the converter renders the RAW first — demosaicing the sensor data and baking in white balance, exposure, and tone — and once that is encoded, the latitude is gone, exactly as it would be in a JPEG. Keep your original .mos as the editable master in Capture One, which replaced Leaf Capture as the processing software for all Leaf Aptus and Aptus-II backs. If you want an archival render rather than a web copy, MOS to TIFF preserves more detail for print and storage.

Will an AVIF keep the full resolution of a medium-format back?

It can, if you let it. A Leaf Aptus back captures far more pixels than a typical web image needs, and by default this converter keeps the original resolution — so the AVIF holds the back's full pixel count. For faster page loads you can downscale under "Image resolution" to a preset such as 1080p or by percentage; for the web, a downscaled AVIF is usually the right call, while the full-resolution master stays in the untouched .mos. AVIF also supports 10- and 12-bit color, so a high-bit-depth render keeps more tonal range than an 8-bit JPEG would.

Why convert from MOS rather than from a JPEG I already exported?

Because AVIF encodes best from a clean source. A MOS is lossless sensor data, so the AV1 encoder sees the real image; encoding from an already-compressed JPEG instead carries that file's existing artifacts into the AVIF, and the result is worse than starting from the RAW. If your goal is the smallest high-quality web image, rendering straight from the .mos gives the encoder the best possible input.

Is AVIF safe to use on the web yet, or should I use JPEG?

AVIF is widely supported: caniuse.com reports about 93% global coverage, with Chrome 85+, Firefox 93+, Safari 16.4+, and Edge 121+ all decoding it. That covers the large majority of visitors, and a 30-50% size saving over JPEG at similar quality is significant for image-heavy portfolios. If you still need to reach very old browsers or email clients, render a universal copy with MOS to JPG and serve AVIF as the primary with JPEG as a fallback.

My MOS file won't decode — what should I try?

MOS comes in uncompressed and compressed variants, and support for the compressed form varies by RAW processor, so an odd file occasionally fails to read. The reliable fallback is to open the .mos in Capture One and export a TIFF, then convert that with MOS to TIFF or feed the TIFF through the Image Compressor to reach AVIF. Note that .mos is the Leaf Aptus format specifically — the later Leaf Credo backs write .iiq files instead, so if your file is actually an IIQ it needs the matching converter.

How are my files handled during conversion?

In our testing, a full-resolution Leaf MOS rendered at the "Very High" preset produced an AVIF a small fraction of the RAW's size, since AV1 compresses a finished still far more efficiently than the sensor data behind it. Your file is uploaded over an encrypted connection, rendered and encoded into AVIF on our servers, and deleted automatically a few hours after conversion — no sign-up, no watermark, never shared or made public. The main practical limit is upload size and time, since medium-format MOS files often run from tens to over a hundred megabytes each.