Phase One introduced IIQ, short for Intelligent Image Quality, in 2008 alongside the P65+ digital back \u2014 part of a line of medium-format camera backs aimed at studio, landscape, and cultural-heritage photography where extremely high resolution and dynamic range matter more than file size or shooting speed. The format was built specifically to handle sensor readouts far larger than typical 35mm-format cameras produce, with current Phase One systems reaching resolutions above 150 megapixels.<\/p>
IIQ comes in two working variants that matter for storage planning: IIQ L applies lossless compression, keeping every bit of sensor data intact for archival-grade capture, while IIQ S applies visually lossless compression that shrinks files by roughly 40 to 60 percent with negligible perceptible quality loss \u2014 a deliberate trade-off for workflows generating enormous data volumes per shoot.<\/p>
Because Phase One remains an active, specialized vendor with Capture One as its flagship processing software, IIQ is comparatively well supported today, and mainstream tools like Adobe Camera Raw track new back releases reasonably closely. Even so, a DAM handling Phase One assets should keep IIQ L files as the true archival master rather than IIQ S, and lean on DNG or fully rendered derivatives for team members without a Capture One license.<\/p>","protected":false},"excerpt":{"rendered":"
IIQ is Phase One’s proprietary raw format for its high-resolution medium-format digital backs, introduced in 2008 and available in lossless (IIQ L) and visually-lossless-compressed (IIQ S) variants.<\/p>\n","protected":false},"author":0,"featured_media":0,"template":"","meta":{"footnotes":"","faq":[{"question":"What are the two IIQ variants and why does the distinction matter for DAM storage budgeting?","answer":"IIQ L uses lossless compression for zero-quality-loss capture, while IIQ S uses visually lossless compression that cuts file sizes roughly 40-60% with minimal perceptible quality impact, directly relevant to storage budgeting for very large medium-format libraries."},{"question":"Which IIQ variant should a DAM keep as the archival master?","answer":"IIQ L, the lossless variant, should be the archival master: it retains the complete 16-bit sensor readout with zero quality loss, and open-source libraries such as LibRaw and RawSpeed have reverse-engineered support for it, so archives stay readable without a Capture One license. IIQ S applies lossy compression and, per LibRaw's own developers, remains undocumented with no open-source decoder in sight, making it a poor long-term preservation choice despite its smaller footprint."},{"question":"What resolutions does IIQ need to accommodate?","answer":"Phase One's large-area CCD and CMOS backs range up to 150+ megapixels in current systems, so a DAM handling IIQ needs to plan storage and preview generation around very large file sizes."},{"question":"Is IIQ decoder support at risk of vendor abandonment?","answer":"Low risk currently. IIQ is a professional, actively maintained format from a currently operating vendor, though Capture One remains the reference tool for full-fidelity processing of high-end Phase One backs."},{"question":"When was IIQ introduced?","answer":"Phase One introduced IIQ in 2008 alongside the P65+ digital back, a 60-megapixel CCD back that was among the highest-resolution medium-format sensors of its era. The format was built to handle large, high-bit-depth captures efficiently. Phase One has kept using IIQ across every digital back generation since \u2014 IQ, IQ3, IQ4 \u2014 as resolution climbed toward 150+ megapixels, preserving the same .iiq extension and L\/S variant split for close to two decades of production cameras."},{"question":"What bit depth does IIQ capture at?","answer":"IIQ captures at 16 bits per channel, matching the native output of Phase One's CCD and CMOS medium-format sensors rather than the 12- or 14-bit depth common on smaller-format cameras. That extra bit depth preserves finer tonal gradation and more shadow\/highlight recovery headroom, valuable when files get pushed hard in post-production. For a DAM, it also means IIQ masters carry more raw data per pixel than typical DSLR formats \u2014 worth factoring into storage capacity planning."},{"question":"Is there a public specification for IIQ?","answer":"No. Phase One has never published an official IIQ specification; everything third-party tools know about the format comes from reverse engineering by projects like LibRaw, RawSpeed, and ExifTool. That work has been thorough enough to cover IIQ L reliably, but IIQ S remains, in LibRaw's own words, undocumented and unsupported by any open-source decoder. For a DAM, this closed-format risk is the strongest argument for generating open, standardized derivatives such as DNG or TIFF alongside the IIQ master, rather than depending indefinitely on third-party reverse-engineering or vendor support."},{"question":"What open-source tools can decode IIQ?","answer":"LibRaw is the core open-source library behind IIQ decoding, and it currently reads IIQ L files only \u2014 IIQ S remains undocumented and unsupported by any open-source decoder. Tools built on that support include darktable, which decodes IIQ through RawSpeed with Phase One-specific handling, and RawTherapee, which relies on libraw-based decoding. For a DAM, this means automated preview generation and integrity checks are possible without a Capture One license, but only for lossless IIQ L masters."}],"checked_date":"2026-08-11","sources":[{"statement":"IIQ is Phase One's proprietary raw format, with IIQ Large using lossless compression and IIQ Small using visually lossless compression that reduces file size by roughly 40-60%","source_name":"Phase One, Intelligent Image Quality (IIQ) overview","url":"https:\/\/www.phaseone.com\/imaging-quality-performance\/intelligent-image-quality-iiq\/","checked":"2026-08-07"},{"statement":"The Phase One P65+ digital back was announced in 2008 and paired with the IIQ raw format","source_name":"Photography Bay, hands-on coverage of Phase One 645DF, P65+ and P40+","url":"https:\/\/photographybay.com\/2009\/10\/22\/hands-on-phase-one-645df-p-65-and-p-40\/","checked":"2026-08-07"},{"statement":"Phase One digital backs shoot IIQ files that are opened natively in Capture One, with Adobe Camera Raw support varying by back generation","source_name":"Capture One support, Phase One RAW files option","url":"https:\/\/support.captureone.com\/hc\/en-us\/articles\/360002564358-Phase-One-RAW-files-option","checked":"2026-08-07"}],"kicker":"","fact_checker":0,"reading_time":0,"revisions":[],"seo_title":"IIQ file: Phase One raw format, compression and converters","seo_description":"","noindex":false,"ext":"iiq","full_name":"Intelligent Image Quality","vendor_name":"Phase One","introduced":"2008, announced with the Phase One P65+ digital back","container_notes":"IIQ stores unprocessed sensor data at 16 bits per channel from Phase One's large-area CCD and CMOS backs, which range up to 150+ megapixels in current systems. It ships in two variants: IIQ L, using lossless compression for zero-quality-loss capture, and IIQ S, using visually lossless compression that cuts file sizes roughly 40\u201360% with minimal perceptible quality impact \u2014 a distinction directly relevant to DAM storage budgeting for very large medium-format libraries. The format embeds camera metadata and preview data but has no public specification.","open_with":[{"platform":"Windows \/ macOS","how":"Capture One, Phase One's own software and the primary professional tool for IIQ, with full support for both compression variants"},{"platform":"Windows \/ macOS","how":"Adobe Camera Raw \/ Lightroom Classic, with support that varies by digital back generation"},{"platform":"Cross-platform, open source","how":"darktable, via RawSpeed with camera-specific additions for Phase One backs"},{"platform":"Cross-platform, open source","how":"RawTherapee, with libraw-based IIQ decoding"}],"archive_advice":"IIQ is a professional, actively maintained format from a currently operating vendor, so decoder abandonment risk is relatively low, but Capture One remains the reference tool for full-fidelity processing of high-end Phase One backs. For DAM archival, keep the IIQ L (lossless) master and generate DNG or rendered derivatives for search, preview, and cross-team access outside Capture One licenses.","related":[2613,2602,2596,2611,2592,2599],"tool_link":""},"silo":[23],"class_list":["post-2612","format","type-format","status-publish","hentry","silo-formats"],"_links":{"self":[{"href":"https:\/\/picajet.com\/articles\/wp-json\/wp\/v2\/format\/2612","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\/2612\/revisions"}],"predecessor-version":[{"id":3670,"href":"https:\/\/picajet.com\/articles\/wp-json\/wp\/v2\/format\/2612\/revisions\/3670"}],"wp:attachment":[{"href":"https:\/\/picajet.com\/articles\/wp-json\/wp\/v2\/media?parent=2612"}],"wp:term":[{"taxonomy":"silo","embeddable":true,"href":"https:\/\/picajet.com\/articles\/wp-json\/wp\/v2\/silo?post=2612"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}