MOS traces back to Leaf, a Massachusetts-based company that shipped one of the earliest medium-format digital camera backs, the Leaf DCB1, in 1991. The MOS extension itself became associated with Leaf’s raw output through the Valeo family of portable digital backs launched from 2002 onward, and continued through later Leaf lines including Cantare, Volare, and Aptus. Leaf built its business specifically around high-resolution backs for Hasselblad, Mamiya, and Contax medium-format camera bodies.<\/p>
Structurally, MOS uses a TIFF\/EXIF base but does not fully comply with the TIFF standard, and it stores raw data as a single grayscale sensor plane \u2014 uncompressed or with JPEG lossless compression \u2014 reflecting the pre-demosaic Bayer data straight off the back’s CCD sensor. Phase One acquired Leaf from Kodak in 2009, and the Leaf and Mamiya brands were later consolidated under Phase One, with subsequent Leaf-branded backs eventually adopting Phase One’s own IIQ format instead of MOS.<\/p>
That corporate history matters directly for archival planning: MOS is now a format tied to hardware nobody manufactures anymore, from a brand absorbed into a larger company years ago. Leaf’s own raw converter software is effectively frozen in time, and while Capture One and Adobe Camera Raw still handle most MOS files, compressed variants from certain Leaf backs are already outside Camera Raw’s support. A DAM holding legacy medium-format archives with MOS files should treat DNG conversion as a near-term priority rather than an eventual nice-to-have.<\/p>","protected":false},"excerpt":{"rendered":"
MOS is the raw format used by Leaf’s medium-format digital camera backs, a TIFF\/EXIF-derived structure that continued in use after Phase One acquired Leaf in 2009.<\/p>\n","protected":false},"author":0,"featured_media":0,"template":"","meta":{"footnotes":"","faq":[{"question":"Why is MOS considered one of the more archivally fragile formats for a DAM?","answer":"MOS is tied to discontinued Leaf digital-back hardware from a brand that no longer exists independently, and Leaf's own conversion software is unmaintained, making it one of the more fragile formats in this list."},{"question":"What happened to the Leaf brand behind MOS?","answer":"Phase One acquired Leaf in 2009, and later Leaf\/Mamiya Leaf backs eventually shifted to Phase One's own IIQ format, making MOS effectively a legacy format tied to discontinued hardware."},{"question":"Is MOS fully TIFF-compliant?","answer":"No. MOS uses a TIFF\/EXIF file structure as its base but is not fully TIFF-compliant, storing raw sensor data as uncompressed or JPEG-lossless-compressed grayscale, single-plane, pre-demosaic images."},{"question":"Does Adobe Camera Raw support all MOS files?","answer":"No. Camera Raw supports uncompressed MOS files, but compressed MOS from some Leaf backs is not supported by Camera Raw."},{"question":"What should a DAM do with MOS assets in a legacy medium-format archive?","answer":"Convert them to DNG proactively, rather than waiting for compatibility gaps to appear in current software, given the format's fragile support situation."},{"question":"What Leaf digital-back product lines used MOS?","answer":"Leaf's Valeo, Cantare, and Volare digital backs, and it continued into the Aptus series."},{"question":"What current software still supports MOS?","answer":"Capture One supports MOS as part of Phase One's unified raw processing after the Leaf acquisition, and darktable via RawSpeed supports Leaf\/Mamiya Leaf backs."},{"question":"When was MOS introduced?","answer":"Circa 2002, with Leaf's Valeo line of digital backs, continuing after Phase One's 2009 acquisition of Leaf."}],"checked_date":"2026-08-07","sources":[{"statement":"Leaf introduced the first medium format digital camera back, the Leaf DCB1, in 1991, and was later acquired by Phase One and an Israeli investor group from Kodak in 2009","source_name":"Fstoppers \/ Wikipedia, Leaf company history and Phase One-Mamiya coverage","url":"https:\/\/en.wikipedia.org\/wiki\/Leaf_(Israeli_company)","checked":"2026-08-07"},{"statement":"The MOS format uses a TIFF\/EXIF file structure but is not fully TIFF-compliant, storing raw images as uncompressed or JPEG-lossless-compressed grayscale data, used by Leaf's Valeo, Cantare, and Volare digital backs","source_name":"Just Solve the File Format Problem (Archive Team wiki), Leaf MOS","url":"http:\/\/fileformats.archiveteam.org\/wiki\/Leaf_MOS","checked":"2026-08-07"},{"statement":"Creo launched the Leaf Valeo family of digital backs in September 2002, with commercial shipments beginning that December","source_name":"ePHOTOzine, Creo launches Leaf Valeo coverage","url":"https:\/\/www.ephotozine.com\/article\/creo-launches-leaf-valeo--a-new-portable-digital-back-family-1020","checked":"2026-08-07"},{"statement":"Adobe Camera Raw does not support compressed MOS and IIQ files from Leaf cameras; proprietary converters such as Leaf Raw Converter and Capture One are needed for those","source_name":"B&H Photo Video, Mamiya Leaf Aptus-II product documentation","url":"https:\/\/www.bhphotovideo.com\/c\/product\/823122-REG\/Mamiya_010_10847A_Leaf_Aptus_II_56_Digital.html","checked":"2026-08-07"}],"kicker":"","fact_checker":0,"reading_time":0,"revisions":[],"seo_title":"","seo_description":"","noindex":false,"ext":"mos","full_name":"Leaf Camera RAW","vendor_name":"Phase One (originally Leaf Systems, acquired 2009)","introduced":"circa 2002, with Leaf's Valeo line of digital backs; continued after Phase One's 2009 acquisition of Leaf","container_notes":"MOS uses a TIFF\/EXIF file structure as its base but is not fully TIFF-compliant, storing raw sensor data as uncompressed or JPEG-lossless-compressed grayscale (single-plane, pre-demosaic) images. It was used across Leaf's Valeo, Cantare, and Volare digital backs and continued into the Aptus series. Leaf became a Phase One-owned brand in 2009, and later Leaf\/Mamiya Leaf backs eventually shifted to Phase One's own IIQ format, making MOS effectively a legacy format tied to discontinued hardware.","open_with":[{"platform":"Windows \/ macOS","how":"Capture One, which supports MOS as part of Phase One's unified raw processing after the Leaf acquisition"},{"platform":"Windows \/ macOS","how":"Adobe Camera Raw \/ Lightroom Classic, for uncompressed MOS files (compressed MOS from some Leaf backs is not supported by Camera Raw)"},{"platform":"Cross-platform, open source","how":"darktable, via RawSpeed with support for Leaf\/Mamiya Leaf backs"},{"platform":"Legacy Leaf native","how":"Leaf Capture \/ Leaf Raw Converter, Leaf's original discontinued software"}],"archive_advice":"MOS is tied to discontinued Leaf digital-back hardware from a brand that no longer exists independently, and Leaf's own conversion software is unmaintained, making this one of the more archivally fragile formats in this list. Convert MOS assets to DNG for any DAM holding legacy medium-format archives, and do so proactively rather than waiting for compatibility gaps to appear in current software.","related":[2605,2600,2590,2610,2591,2598],"tool_link":""},"silo":[23],"class_list":["post-2613","format","type-format","status-publish","hentry","silo-formats"],"_links":{"self":[{"href":"https:\/\/picajet.com\/articles\/wp-json\/wp\/v2\/format\/2613","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/picajet.com\/articles\/wp-json\/wp\/v2\/format"}],"about":[{"href":"https:\/\/picajet.com\/articles\/wp-json\/wp\/v2\/types\/format"}],"version-history":[{"count":3,"href":"https:\/\/picajet.com\/articles\/wp-json\/wp\/v2\/format\/2613\/revisions"}],"predecessor-version":[{"id":3671,"href":"https:\/\/picajet.com\/articles\/wp-json\/wp\/v2\/format\/2613\/revisions\/3671"}],"wp:attachment":[{"href":"https:\/\/picajet.com\/articles\/wp-json\/wp\/v2\/media?parent=2613"}],"wp:term":[{"taxonomy":"silo","embeddable":true,"href":"https:\/\/picajet.com\/articles\/wp-json\/wp\/v2\/silo?post=2613"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}