PNG to ORF Converter

Encoding: the PNG uses lossless DEFLATE with a prediction filter chosen per row; 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: 1, 2, 4, 8 or 16 bits per channel in the PNG; ORF allows 12 bits per channel, and the DNG written here has 8 bits per channel, linearised. 16-bit PNGs from photo and scientific software are reduced to 8 bits per channel.

Colour: RGB, greyscale, or an indexed palette of up to 256 colours in the PNG; ORF supports camera RGB from a Bayer mosaic, written here as 8-bit sRGB.

Transparency: the PNG stores it as a full alpha channel, so edges and shadows can fade smoothly; the DNG has none, so transparent areas are filled with the colour you choose.

Metadata: the PNG can carry text chunks, an ICC profile, physical resolution and EXIF in an eXIf chunk; ORF can carry EXIF and Olympus maker notes, which also contain the preview, but nothing is copied across.

PNG stores pixels losslessly with full alpha transparency. It is ideal for screenshots, logos, UI and anything with sharp edges, but photos saved as PNG are several times larger than JPEG.

A PNG opens with an 8-byte signature and is a chain of chunks, each with its own CRC: IHDR (size, depth, colour type), optional PLTE and tRNS for palettes, one or more IDAT chunks with the compressed rows, and IEND.

PNG files usually come from screenshots, design exports, logos and web graphics.

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 PNG 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.