File formats - BMP / RAW

Every digital image is a bitmap (BMP) or matrix of adjacent pixels. If you would enlarge a small area of a bit-mapped image you would clearly be able to see the pixels it is made up of. Together these pixels form a massive grid that creates the illusion of a continuous tone image. The number of pixels in this matrix determines the size at which such an image can be printed or displayed. Because saved bitmap files are quite large in size other graphic formats are used to store images in compressed format.

Some digicams let you save the raw image data straight from the CCD in an uncompressed file format called CCD RAW. This format contains all the information as captured by the CCD as no in-camera processing is performed. It can be transferred to a computer where the data can be worked on to produce the final image. Advantages are its smaller file size as written by the camera, shorter intervals between exposures, plus of course optimum image quality since no data is lost through compression. A disadvantage is that it can't be opened by image manipulating programmes without using a plug-in such as TWAIN. Canon was the first to introduce this format, but as yet there is no universally accepted RAW format, each manufacturer maintains his own standard.