What is RAW?

[timtam]

What exactly is it? I know that it's suposed to be the best quality of a pic or something... but I need some more info? If someone can please explain I would be most delighted! lol

[Desmond]

I can send you a pic of me in RAW if you like. :eek: LOL

Seriously though...

Basically that file is what the sensor sees - no or minimal processing.

The longer explaination is below for those who are interested ;)


Raw files contain pixel data from the image sensor usually at 12 or 14 bits per individual sensor bucket. These pixels are a mosaic of either red, blue or green values. The sensor is filtered with dye to direct the correct color of light into each bucket, this is called a Bayer filter (http://en.wikipedia.org/wiki/Bayer_filter). To retrieve an image from a RAW file this mosaic must be converted into an RGB image. This is known as Demosaicing (http://en.wikipedia.org/wiki/Demosaicing), but this process is referred to by many manufacturers as Digital Development.
The contents of RAW files are often considered to be of 'higher quality' than the RGB converted results. Each pixel in RAW is represented by a higher range number. Transformations which affect brightness or color curve lose less information when performed on the raw data. This does not mean that an 8Mb RAW file is of higher quality than an 8Mb RGB file. It simply means that less information is lost in these particular transformations.

RAW permits much greater control than JPEG for several reasons:

Finer control is easier for the settings when a mouse and keyboard are available to set them. For example, the white point can be set to any value, not just discrete values like "daylight" or "incandescent".
The settings can be previewed and tweaked to obtain the best quality image or desired effect. (With in-camera processing, the values must be set before the exposure). This is especially pertinent to the white balance setting since color casts can be difficult to correct after the conversion to RGB is done.
Camera raw files have 12 or 14 bits of brightness information. But you cannot compare this number alone to other methods. JPEG stores a brightness gradient in an 8-bit number every 4 or 8 pixels and stores color values even more infrequently depending on the parameters used. Because of this JPEG loses fine details and is ill-suited for major color or brightness changes. By comparison the mosaicing used by the Bayer filter in raw files changes colors every 3-4 pixels and brightness every 1-2 pixels producing much finer resolution detail in a same size image. And because it is 12-bit each of these values are far more precise.
The working color space (http://en.wikipedia.org/wiki/Color_space) can be set to whatever is desired.
Different demosaicing (http://en.wikipedia.org/wiki/Demosaicing) algorithms can be used, not just the one coded into the camera.