.DNG

Adobe Digital Negative

Introduction

DNG is an open raw image format published by Adobe in 2004. Most camera makers use a raw format of their own; DNG gives raw photos a single documented format that any program can read, with everything needed to develop the image stored in the file itself.

Some cameras and phones save DNG directly, including models from Leica, Pentax and Ricoh and the Apple ProRAW mode of recent iPhones. Adobe’s free DNG Converter turns other raw files into DNG.

Software

Structure

A DNG file is a TIFF file, with the same header and image file directories, and extra tags defined by the DNG specification. The DNGVersion tag marks the file as DNG. The first directory usually holds a small preview image and the metadata, and the raw sensor data sits in a sub-directory marked as the full resolution original.

Tags carry what a raw converter needs to develop the picture: the colour filter pattern of the sensor, black and white levels, colour matrices for two light sources, lens corrections and optional camera profiles. The raw data may be uncompressed or compressed without loss, and newer versions add lossy and JPEG XL compression.

  1. 0TIFF header byte order, 42, first IFD offset8 bytes
  2. …IFD 0 preview image, DNGVersion, colour and camera tagsvaries
    1. …Sub-IFD the raw sensor datavaries
    2. …Exif IFD exposure, lens and datevaries
A DNG file: TIFF directories with the raw data in a sub-IFD