A software file used in colour management processes that describes the properties of a specific device so that your computer can correct or ‘normalise’ the way it displays or prints colours. If you don’t use colour management in your workflow, you don’t need to worry about this.
This is the system used by computers and other digital devices for defining colours. In photography, the RGB system is almost universal – colours are defined using red, green and blue colour ‘channels’. In printing, it’s CMYK, or cyan, magenta, yellow and black. Some image-editing processes use Lab mode, which consists of a ‘lightness’ channel and two (‘a’, ‘b’) colour channels.
For designers and professional photographers it’s often important to maintain consistent colour rendition from the camera, through to the computer display used for browsing and editing photos and right through to the final output device, generally a printer. Colour management tools use software ‘profiles’ and hardware monitor calibration and printer calibration devices to try to ensure this consistency of colour. It’s a complex process, and it’s worth pointing out that when images are going to be displayed on a screen rather than being printed, you have no control over the colour rendition of the output device. Many photographers don’t use colour management at all.
This is a colour model used in printing processes, where colours are defined in terms of cyan, magenta, yellow and black colour channels (black is represented by the letter ‘K’). Desktop printers use CMYK inks but carry out the conversion from regular RGB photos automatically. In commercial printing, a designer will convert a regular RGB photo to CMYK to check the colour rendition and prepare it for printing.
This is a professional colour space offered by more advanced cameras and it captures a slightly wider range of colours than the usual sRGB colour space used by most consumer devices. It can be useful if pictures are destined for commercial print production, but it does introduce complications with colour profiles and monitor calibration.