File extension
.crw
Canon Raw (CRW) format
.crw files are the original Canon Raw format: an early camera raw format based on the Canon CIFF container, used by Canon's first digital SLRs and PowerShot models before the later CR2 and CR3 formats.
Known meanings
Formats and reference material for .crw
Canon Raw (CRW) format
Canon's original camera raw image format, based on the CIFF container
Details
Format notes
Canon Raw (CRW)
CRW is Canon’s original digital camera raw format, used by early EOS digital SLRs (such as the D30, D60, and 10D) and various PowerShot cameras. Like later Canon raw formats it stores minimally processed sensor data plus capture metadata, allowing white balance, exposure, and color to be decided during raw development rather than at capture time.
Where the later CR2 is based on TIFF and CR3 on the ISO Base Media File Format, CRW uses Canon’s own Camera Image File Format (CIFF). CIFF organizes the file as a hierarchy of typed records within a heap, holding the raw image data, a thumbnail or preview, and camera settings and shooting information. CRW predates the widespread EXIF-in-raw convention, so metadata lives in these CIFF records rather than a standard EXIF block.
Legacy Status And Tooling
CRW was superseded by CR2 and then CR3, so it is primarily encountered as a legacy format from older Canon equipment. Because CIFF was documented and further reverse-engineered, tools such as ExifTool, dcraw, and LibRaw can read CRW files, extract their metadata, and decode the raw image. As with any raw format, the developed appearance depends on the converter’s demosaicing and color handling.
Preservation Notes
Being an obsolete, camera-specific raw format, CRW is a candidate for migration
risk. For preservation keep the original .crw, record the camera model, and
consider producing a documented derivative such as DNG or a rendered TIFF while
retaining the CIFF metadata (white balance, exposure, and lens information)
that is needed to reprocess the image.
Security Notes
A CRW parser reads nested CIFF records with offsets and lengths that, in an untrusted file, may be malformed. Validate record boundaries, heap offsets, and image dimensions before allocating buffers or decoding to avoid out-of-bounds access and excessive memory use.
Further Reading
- Canon CRW / CIFF format notes:
https://exiftool.org/canon_raw.html - LibRaw (raw decoding library):
https://www.libraw.org/