RGB

RGB stands for red, green and blue, the three colour ‘channels’ that go to make up all the colours in a digital image. It comes in two varieties – sRGB is a ‘universal’ RGB that can be used and displayed by any device, whereas Adobe RGB is a more specialised alternative for pros.

Printer calibration

Printers don’t always produce accurate colours, particularly when using third-party papers or inks. A printer calibration kit will measure the colours produced by the printer and then create a software printer profile which adjusts the colour data sent to the printer.

Monitor calibration

Monitors rarely display colours with complete accuracy, so some professionals use calibration kits that use a sensor to read the monitor’s colours and then apply a software profile to correct the display.

Colour space

Different devices can’t always display the same range of colours, so your camera may be able to record a wider range of colours than your computer monitor or tablet can display, for example – in other words, the monitor offers a smaller ‘colour space’. To get round this, there are two main RGB colour spaces you can work on. The sRGB colour space is a smaller, universal colour space that practically any device can match. Adobe RGB is a larger colour space that your camera and printing systems can capture but your monitor probably can’t, which means some complex workarounds and pitfalls and really needs a switch to a more complex colour managed workflow. sRGB is the simplest solution, and (though some will debate this) you’re unlikely to see any real advantage to Adobe RGB in everyday photography.

Colour profile

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.

Colour model

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.

Colour management

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.

CMYK

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.

Adobe RGB

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.