A Raw file is…
• not an image file per se (it will require special software to view, though this software is easy to get).
• typically a proprietary format (with the exception of Adobe’s DNG format that isn’t widely used yet).
• at least 8 bits per color – red, green, and blue (12-bits per X,Y location), though most DSLRs record 12-bit color (36-bits per location).
• uncompressed (an 8 megapixel camera will produce a 8 MB Raw file).
• the complete (lossless) data from the camera’s sensor.
• higher in dynamic range (ability to display highlights and shadows).
• lower in contrast (flatter, washed out looking).
• not as sharp.
• not suitable for printing directly from the camera or without post processing.
• read only (all changes are saved in an XMP “sidecar” file or to a JPEG or other image format).
• sometimes admissable in a court as evidence (as opposed to a changeable image format).
• waiting to be processed by your computer.
In comparison a JPEG is…
• a standard format readable by any image program on the market or available open source.
• exactly 8-bits per color (12-bits per location).
• compressed (by looking for redundancy in the data like a ZIP file or stripping out what human can’t perceive like a MP3).
• fairly small in file size (an 8 megapixel camera will produce JPEG between 1 and 3 MB’s in size).
• lower in dynamic range.
• higher in contrast.
• sharper.
• immediately suitable for printing, sharing, or posting on the Web.
• not in need of correction most of the time (75% in my experience).
• able to be manipulated, though not without losing data each time an edit is made – even if it’s just to rotate the image (the opposite of lossless).
• processed by your camera.
