Spectral photometers (or spectrophotometers) are high-quality colorimeters that can measure and accurately describe any colour.
The measuring instrument achieves this by illuminating the measuring surface with the entire spectrum of the visible light. The remission values of certain wavelengths together give the measured value, often this is output in Lab (measuring mode freely selectable from M0 to M2). The spectral measurements can also be stored directly.
High-quality proof printers have their own spectrophotometers to verify the print directly.
Colour measurement is used to determine the exact colour location of a colour in a colour system.
There are three methods:
The Tristimulus Method:
A tristimulus colourimeter shines an internal light source onto the surface of the colour sample.The reflected light passes through three filters – red, green and blue – which determine the intensity of these color components.
The reflected light passes through three filters – red, green and blue – which determine the intensity of these colour components.
The Spectral Method:
A spectrophotometer works in a very similar way – but has not only three, but 31 filters that measure 31 different wavelengths of the reflected light. Thus the spectral method is one of the best methods for measuring colour.
Here, a measuring device (or the eye) is used to compare the colour sample with standard colour samples until all samples are considered identical by the observer. However, this is assessed subjectively by the viewer, which is why the other methods of colour measurement are preferred in practice.
With colour management it can be achieved that colours on different devices like cameras, scanners, monitors, laser, inkjet, offset printers and many more can be reproduced as similar as possible to each other.
Therefore device-dependent colour spaces must be used. A well working colour management will map the gamut of each device as Monitores and printer and device-independent colour spaces such as Adobe RGB 1998
Modern colour management systems use instruments such as the X-Rite i1 Pro 2 and related colour management software that creates and manages colour profiles within application programs such as the Adobe product range provides.