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The choice of colour models is one of the basic themes in the area of design and printing and it has high significance.


The choice of colour models is one of the basic themes in the area of design and printing and it has high significance. This is owing to the characteristics of each participant of the production stages of printing materials – photographers, designers, pre-print and print. Each of them is using different colour space in their daily life but in order to have portability of the files they should be prepared for the next stage in a certain manner. That is why the choice of the right colour model is essential.

This is the moment to point out that the screens, scanners, projectors and the digital cameras use the RGB models while the professional printing machines use CMYK. Each separate device has a different colour range (space) which is just a part of the spectrum of the visible colours. Since the colour spaces do not entirely coincide, one colour may look differently on the separate devices. The colour models have different ranges. 

 

LAB

LAB is an interesting model which is independent on the characteristics of the monitor and the output devices. LAB is introduced in 1976 by the International commission     on illumination (CIE) (also reffered to as CIELAB because of the combination CIE+LAB). LAB turns out to be the best colour models. The reason behind this is that LAB is the only system with equal contrast and it maintains the same colour visualization disregarding the characteristics of the device. 

LAB has three components: L – Luminosity; a – conversion from red to green; b – conversion from blue to yellow. ‘L’ is measured in percentages while ‘a’ and ‘b’ have numerical values from 120 to +120. When ‘L’ is 100% and the values of ‘a’ and ‘b’ = 0 you have white colour. When ‘L’ = 0 red colour appears.

The colour model LAB is made up to resemble the human vision and the luminosity ‘L’ resembles the human perception of lightness. This model contains in its colour space all visible (RBG and CMYK) colours and it is independent on the lightness and the pigments.

LAB fills in the gaps in the two other models (RGB and CMYK). Working with it guarantees that the file will be open on another computer the same way you have given it. There will not be any losses of colour.

However, it is not possible the final image to remain in LAB. Using this colour model is an intermediate before converting the image into RGB and CMYK. The conversion to RGB is recommended when working with a digital presentation while working with CMYK colours – when preparing images for printing. 

 

RGB

RGB color model is used to describe colours which derive from sources of light. It uses combination of R – red, G – green and B – blue lights with different brightness ratio for deriving each different colour in its spectrum. RGB model is relatively close to the human perception as the human eye has receptors which react to these colours. The three of the colours are called additive (stimulating) and when they overlap – the result is white. Owing to the characteristics of the model, it is suitable for using when working on web design and video.

 
 

 

 

 

CMYK

Contrary to the RGB model, when working with CMYK white background (printing on paper or cardboard) and darkening by mixing colours are being used. In CMYK model combinations of the following subtractive colours are used: C – Cyan, M – Magenta, Y – Yellow and К – Key (black). When combining the three colours we have black which the so called composite black in the printing. This model is best to be used by printing media which uses vector subjects and texture. A compromise could be made when working with binary images which could be processed in the RGB model since the result is being observed on a screen. However, in the end – before their printing, the images should be transformed into CMYK model. This results in losses since the colour range of RGB is wider than the one of the CMYK model.

 

 

 

Visualization of the colours on a screen

Please mind the fact that there are technically-based differences between the visualization of the clours on  screens and printings of the colours when compared to the original sample of the colour charts. RGB and CMYK values cannot guarantee the literal presentation of the colours. However, when using well calibrated devices, the presentation of the colours is very close to the true results.  Owing to this fact, the orders of colored products should be made after choosing from the original true colour chart.