Raw files and DNG
September 2004 (Adobe DNG)
Raw files keep the sensor’s data before processing, so photographers can decide on white balance and tones later. Adobe’s DNG offered an open format for them.
How it began
Cameras turn sensor data into a JPEG using fixed settings. Professional cameras could save the unprocessed data, the raw file, in formats specific to each maker. In 2004 Adobe published DNG, an open format for raw data.
How it works
The raw file holds the values from every photosite under the Bayer filter, usually 12 or 14 bits each. Software does the demosaicing, sets the white balance and applies a tone curve, and the photographer can redo these at any time.
Why it mattered
Raw editing became the digital darkroom: more room to correct exposure and colour, without losing quality. DNG was intended to keep files readable when makers dropped formats.
Limits and what replaced it
Files are large and need processing. Most makers still use their own formats; phones mix raw data with computational processing.
Today
Every serious camera, and many phones, can save raw; DNG is used by many phones and some cameras.