Colorimetry, or colour theory, is the science of colour.
Colorimetry is primarily concerned with an objective and measurable evaluation and definition of colour valences (the visual perception of colour), as well as their relationships to one another.
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.
A colour measuring device for measuring/comparing colours.
It is often used for the calibration of monitors or in biology/chemistry for analysis. More powerful devices, such as the spectrophotometer, can measure colours spectrally and are also used, among other things, for proofs to verify or calibrate printers.