A RAW file is referred to as being a true digital negative. The ability to shoot RAW is found on advanced and professional digital cameras. With a RAW image file, nothing is done by the camera such as sharpening or white balance. This means that the photogrpaher has full control over the image when being edited in Photoshop for example.
RAW is not used widely and can only be opened by certain image editors. Because there is no work done by the digital camera, these files are often very large in size and there for take longer to open on most computers. Having said that a RAW image will have a smaller file size than TIFF images. They would have a .raw extension if this format was used.
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