A raw image (sometimes called RAW, but the term raw isn’t an acronym, but rather a descriptor) is a digital file that consists of pure, unmodified image sensor data. They represent an image. A traditional image is composed of an array of pixel content.
Raw images give you the highest levels of quality, since they haven’t been touched before. They record the most values of brightness and color. Raw’s only drawback is it’s large file size.
How do you shoot raw images?
In order to shoot raw images, you need a camera/device that supports shooting raw. Most entry-level point-and-shoot cameras do not offer this, while most upper end point-and-shoots, and nearly all interchangeable-lens cameras (including mirrorless cameras and DSLRs) have support for saving the images you take in a raw format. Even newer iOS and Android versions support raw imaging nowadays.
For practically all dedicated cameras (cameras that are cameras only) that support raw, you will be able to shoot raw by a flick of a switch in settings. You may even be able to shoot raw + JPEG. The implementations of raw.
Demosaicing raw images
The process of demosaicing turns a raw image into a viewable image. Technically speaking, demosaicing is the algorithm that is used to interpolate for a full color image from the incomplete color samples output from an image sensor overlaid with a color filter array (CFA).
Raw images are overlaid with a color filter array, usually a Bayer array.
Almost all different versions
DCRaw is a popular, open source raw image demosaicer written by Dave Coffin. Virtually all open source raw editors have DCRaw somewhere in the equation, since it is so comprehensive and powerful. In order to use DCRaw, you must download it and compile it. However, nobody uses
Editing raw images
Implementations of raw files
Raw files have different implementations based on the device manufacturer. Adobe has tried to make a uniform standard for raw images, called the DNG (Digital Negative) format, which has been adopted by many camera manufacturers. Otherwise, raw is a concept, not a practical implementation.
Here are just some examples of:
Nikon – NEF files
Canon – Initially CRW, but now CR2
Sony – ARW files
iOS & Android – DNG (this varies based on app but basically all apps use DNG)
Editing raw files
In order to edit raw files, you have to load them up in an editor, which has a demosaicing algorithm built into it. A good example of this is Adobe Lightroom. This is the most popular raw image editor/convertor out there.
Here are some other examples of raw editors/convertors:
- Capture One – A very high quality raw developer made by Phase One
- DXO Optics – Raw editor that places strong emphasis on the hardware of your cameras
- Iridient Developer – A specialty raw editor for Macs only; there is another version for Fuji X-Trans sensors
- DarkTable – Free and open source raw editor (uses DCRaw)
- RawTherapee – Another open source editor, but RawTherapee is of much higher precision and quality (uses DCRaw)
Raw images are unprocessed files that “document” the data that the image sensor has gotten.