ARW to ORF Converter

Encoding: the ARW uses Sony's lossy compressed raw, uncompressed (since the A7R II) or lossless compressed (since the A1); ORF uses losslessly compressed sensor data, with a preview and thumbnail, and the download is a Linear DNG: demosaiced 8-bit RGB with the colour matrices raw editors need.

Bit depth: 12 or 14 bits per channel in the ARW; ORF allows 12 bits per channel, and the DNG written here has 8 bits per channel, linearised. The sensor's 12 or 14 bits are not used: the 8-bit camera preview is converted.

Colour: camera RGB from a Bayer mosaic in the ARW; ORF supports camera RGB from a Bayer mosaic, written here as 8-bit sRGB.

Metadata: the ARW can carry EXIF, Sony maker notes, a thumbnail and a full-size JPEG; ORF can carry EXIF and Olympus maker notes, which also contain the preview, but nothing is copied across.

ARW is the raw format of Sony Alpha, RX and Cyber-shot cameras. It stores the sensor data (compressed, uncompressed or lossless compressed, depending on the model) with a full-size JPEG preview.

ARW is TIFF-based: the first directory carries EXIF and Sony's JPEG preview and the sensor data sits in a sub-directory. In Sony's classic compressed raw each block of 16 same-colour pixels keeps an 11-bit maximum and minimum plus 7-bit steps for the rest, which can leave artefacts beside high-contrast edges.

ARW files usually come from Sony Alpha mirrorless and SLT cameras, RX compacts and some Cyber-shot models.

ORF is the raw format of Olympus and OM System cameras, built around Four Thirds and Micro Four Thirds sensors. It stores 12-bit sensor data with a JPEG preview kept inside Olympus's maker notes.

ORF looks like TIFF but replaces the version number 42 with the letters 'RO', so a little-endian file starts 'IIRO' and generic TIFF readers reject it. Its JPEG preview is not in the main image directory but inside the camera-settings block of Olympus's maker notes.

ORF files come from Olympus E-series DSLRs, OM-D and PEN mirrorless cameras and OM System bodies.

Forms and workflows that ask for ORF usually feed a raw editor, and each of those opens DNG as well, so the DNG can take the ORF's place. Keep the ARW if you only need to view or share the picture.

What ORF offers when it comes straight from the camera: Compact files from a smaller Four Thirds sensor; High Res Shot results stored as a single file; Supported across two decades of Olympus and OM System bodies. Its drawbacks: An 'IIRO' header that generic TIFF readers reject; 12-bit depth, less than most full-frame raw files; A preview hidden inside the maker notes.