RAW IMAGE FORMAT

Definition: The most common image format amongst digital cameras is JPEG, it's a format which produces relatively small files from large amounts of image data by discarding certain information, as JPEG uses a "lossy compression algorithm". The only other common alternative is TIFF, this produces an uncompressed 24-bit per pixel image often in the multiple megabytes, certainly for a 3 megapixel camera in excess of 8 MB per image, not really practical. Each pixel of a CCD can only see one colour, depending on the CFA (colour filter array) placed over the CCD this is either Red/Green/Blue or Cyan/Magenta/Green/Yellow. The cameras internal image processing engine then interpolates colours from the value of neighboring pixels to calculate a full 24-bit colour for each pixel. RAW is simply the raw data as it comes directly off the CCD, no in-camera processing is performed. Typically this data is 8, 10 or 12 bits per pixel. The advantage being that file sizes are considerably smaller (e. g. 2160 x 1440 x 12 bits = 37,324,800 bits = 4,665,600 bytes), the image has not been processed or white balanced which means you can correct the image, and it's a better representation of the "digital negative" captured. The disadvantage is you can't open these image files with a normal photo package without using an "acquire module" (a plug-in, typically TWAIN, which can open / process such images). Advantages of RAW format A true "digital negative", untouched by cameras processing algorithms No sharpening applied No gamma or level correction applied No white balance applied No colour correction applied Lossless yet considerably smaller than TIFF Records data over a wider bit range (typically 10 or 12 bits) than JPEG or 8-bit TIFF Disadvantages of RAW format Requires proprietary acquire module (typically TWAIN) or plug-in to open images Images can take 20-40 seconds to process on an average machine No universally accepted RAW standard format, each manufacturer (even each camera) differs.