Raw image format (Olympus)

ORF (Olympus Raw Format) is the raw format of Olympus cameras and of their successors sold under the OM System brand. You get ORF files from PEN and OM-D models such as the E-M10, E-M5 and E-M1, from the OM-1 and OM-5, from Tough TG compacts and from the old Four Thirds E-series SLRs. The format has outlived the Olympus name: since January 2021 the camera business belongs to OM Digital Solutions, and its cameras still write .ORF.

History

Olympus used ORF as early as the E-10 of 2000, an SLR-style camera with a fixed lens. The E-1 of 2003 started the Four Thirds system, and from 2008 the smaller Micro Four Thirds took over, developed together with Panasonic. Through all those years the extension stayed the same while the content changed with each sensor generation. Olympus never published a specification.

How ORF is built

• A TIFF with a twist. The structure is TIFF, but the first bytes read IIRO, IIRS or MMOR instead of the TIFF signature. Plain TIFF readers therefore reject ORF even though everything inside is familiar.
• 12-bit sensor data. Depending on the model it is stored packed, unpacked in 16-bit words, or compressed with Olympus's own lossless method. There is no lossy option and no choice of raw size.
• Rich maker notes. Picture mode, Art Filter, gradation and the lens correction data are recorded as metadata. A full-size JPEG preview is embedded.
• High Res Shot. Since the E-M5 Mark II (2015) the camera can shift the sensor between several exposures and merge them. On the E-M5 Mark II the resulting ORF has 64 MP and about 100 MB, against 16 MP for a normal shot. The E-M1X (2019) added a handheld version.

Lens corrections are not optional

Micro Four Thirds was designed so that some distortion and vignetting are corrected in software. Compact zooms and pancake lenses in particular rely on it. The correction data travels in the ORF, and Lightroom, OM Workspace and darktable apply it. A raw converter that ignores it shows a slightly wider frame with visible barrel distortion and darker corners. This is the most common reason why an ORF looks "wrong" in a basic viewer.

How to open ORF files

• OM Workspace (Windows, macOS, free for camera owners): the official program, successor of Olympus Viewer and Olympus Workspace. It can apply Art Filters to raw files afterwards and processes High Res Shot files.
• Windows 10 and 11: Photos and File Explorer, after installing the free Raw Image Extension from Microsoft Store.
• macOS and iOS: Preview and Photos, for cameras on Apple's list.
• darktable, RawTherapee (free, also Linux), Lightroom and Photoshop through Camera Raw.

Common ORF problems

ORF won't open in Photoshop or Lightroom

The Camera Raw version predates your camera. Update it, or convert the files with the free Adobe DNG Converter.

Windows 11 does not show ORF thumbnails

Install the Raw Image Extension. Without it Windows only shows a generic icon.

Art Filter missing in the ORF

Art Filters and picture modes are applied only to the camera's JPEG. In the ORF they are just a note. OM Workspace can re-apply them, other programs ignore them.

High Res Shot ORF can't be opened

Many third-party tools support only normal ORF files from a given camera. Use OM Workspace or a current version of Lightroom.

Converting ORF

People convert ORF to JPG for sharing, to TIFF for software without raw support, and to DNG for archiving. Our converter decodes ORF using the camera's white balance and automatic brightness, then saves JPG at quality 90, PNG or 8-bit TIFF in sRGB. Lens corrections and Art Filters are not applied, so expect the distortion described above with some lenses. When the look matters, develop in OM Workspace and export from there. High Res Shot files often exceed our limit of 100 MB per file, and brand-new models may not be supported yet. Raw formats in general are explained on the camera RAW page.

ORF at a glance

More: the OM Workspace download page and the Library of Congress overview of camera raw formats.