RAL DESIGN

The RAL DESIGN System

Although the RAL CLASSIC colours are still very useful, 90 years after their introduction the second, larger RAL colour system is still fairly unknown.

This is entirely unjust due to the fact that with 1688 colour tones the RAL DESIGN System not only offers a larger colour variety, but also particularly pleases with its convincing systematic buildup. The advantage is not only of a theoretical nature, rather it offers the colour design new, expanded, and easy to manage possibilities.

The RAL DESIGN System was developed in 1993 with the guidance of Dr. Ludwig Gall who was at that time the head of the the colour lab at BASF.

The number of colours

The 210 colour tones of the RAL CLASSIC colour collection are, in practice, long insufficient. Manufactured colour systems such as Sikkens 3031, Caparol 3D, Brillux Scala, Pantone, NCS contain approximately 1000-2000 colour tones.

Currently the RAL DESIGN System contains 1688 colour tones. This is more than Pantone (1025), Caparol 3D (1186) and Brillux Scala (1306) and a little less than NCS (1950). With the high number of colours one can achieve a good range of variation, and despite the fact that the RAL DESIGN fans contain sufficiently large colour samples they remain manageable.

The CIELAB-Definition of the colours

RAL DESIGN colours are defined as CIELAB coordinates. Instead of, as is customary, measuring colour ranges after the formula has been identified, the RAL DESIGN colours were designated in advance as CIE-HLC-values in order to then determine the forumlas from those values.

The formulated CIELAB-colours were laid on, reviewed and if necessary reformulated. For some colour tones this process was repeated up to eight times, the end goal is that the colour that „should be“ and the colour that „is“ have a gap of no more than Delta E=0.7.

Descriptive and clear colour names

The RAL DESIGN colour names are very comprehensible. They are comprised of 7 digits and follow the „RAL HHH LL CC“) diagram. Within which the following holds true...

H (Hue): the primary colour hue
The angle in the CIELAB-colour wheel, a value between 010 and 360 degrees, is standardized to three digits. 000 represents the grey colours.

L (Lightness): the CIELAB-lightness
A value between 0 (black) and 100 (white), that can be understood as a lightness percentage.

C (Chroma): the saturation or level of chroma
This is the intensity of a colour with values ranging from 0 (grey of the given lightness) to ca. 60 or 90. The maximum value varies depending on colour area, lightness and pigmentes used.

An example: The designation RAL 240 80 20 indicates the primary colour blue (H=240) with a high lightness of 80 and a low saturation of 20. It is also a pastel blue. If one takes the time to familiarize oneself a little with the build up of the colour wheel one quickly learns the way around the RAL-DESIGN-colours.

A further advantage of the HLC- notation is that a RAL-DESIGN-colour is easy to reproduce from its name alone whether it is as a dispersion, acrylic, for moniter representation or in print. The CIELAB-colour system is available world wide as a production standard in all of these areas.

Thus it is not necessary to ship the RAL DESIGN colour samples anymore. The designation „RAL 120 50 70“ is more than sufficient, for example, for a Chinese manufacturer to finish the product in the accurately selected powerful orange colour.

Systematically arranged colours

For every 10°- step the RAL DESIGN system divides the hue-colour wheel into 36 primary colours. Since the yellow- and orange areas in CIELAB are a little under represented compared to our perceptions, three pages were added in (Hue=75, 85, 95).

Every primary colour is then modified in equal chroma- and lightness-steps from Delta E=10. Given that yellow-red, unsaturated colours are the most useful in facade design, the inside unsaturated area was varied in smaller saturation steps from Delta E=5.

In this manner the RAL DESIGN system overall contains 1688 colour tones that cover the CIELAB-colour space in very regular and equal steps. For the practical colour planning this means that for every colour in every direction neighboring colours and steps can be found that are at the most removed by Delta=10.

Corresponding calculations for colour planning are very easy with the RAL DESIGN systems, as the following examples show:

Lightness graduation example for RAL 240 80 20 (the already given pastel blue) darker additions should be found. RAL 240 60 20, RAL 240 40 20 and RAL 240 20 20 are three variations with the lightness of 60, 40 and 20. The solution is not just a mathematical equal graduation, rather it is also a visual solution as the equivalence with our perceptions is realized as closely as possible in the definition of the CIELAB-colour space.	Lightness graduation RAL 240 80 20
Complementary contrast example for RAL 280 80 20 three contrast colours of the same lightness and saturation are to be found. The four colours measure the colour wheel (360°) in 90-degree-intervals (360°/4). The results are RAL 190 80 20, RAL 100 80 20 and RAL 010 80 20. The fact that the complementary contrast is in point of fact harmonic is due to the CIELAB-colour system satisfying perceptions.	Even a contrast colour can be easily determined with RAL DESIGN.
Transition colour example We are searching for three transition colours between RAL 240 80 20 and RAL 160 40 40. The differences in H, L and C are to be divided accordingly. The results are: RAL 220 70 25, RAL 200 60 30, RAL 180 50 35 as in between colours.	A harmonic colour transition – very easy with RAL DESIGN.

RAL DESIGN colours as CIELAB-representatives

One could point out that the above examples were cleverly chosen so that the resulting colours are alway real available RAL DESIGN colours. If, for example, during the lightness graduation only two in between colours were requested then the resulting graduation would be „bent“ L-values that are not contained in the RAL DESIGN system.

To this point: the RAL DESIGN colours are to be understood simply as selected HLC-representations of the CIELAB colour space. Of course every value between the RAL DESIGN colours also clearly defines the according colour. Even interim values with decimal points do not represent a fundamental problem. It is only to be kept in mind that colours such as „RAL 213.5 77 23.7“ will not be published from RAL as an original paint sample.

Computer application

These days colour design takes place almost exclusively on the computer. The RAL DESIGN system is practically predestined for this use as you can

• calculate with the colour names. Not only the simple examples from above are possible, but rather also complicated problems such as the limits of the colourspace, colour body, or dynamic non-linear colour development.

• that is likewise based on CIELAB „colour management“ and Windows and Macintosh provide for a correct reproduction of the RAL DESIGN colours on monitors and printers.

• Many design programs allow for the direct input of RAL DESIGN colours (as HLC- or Lab-colour values).

• RAL makes the RAL DESIGN colours available for immediate use with the most important design programs, from CorelDRAW to 3D Studio, from Photoshop to Illustrator, through the RAL DIGITAL software. A total of approximately 30 software programs are supported.

Conclusion

The RAL DESIGN system can be easily understood as a modern, structured, and ground-breaking colour system.

Information about the CIELAB colour model

The CIELAB colour space Today CIELAB-colour values have been implemented in the industrial practice in both colour inspections and formulas. The definition from 1976 is a further development of the „table of colours norm“ of the Commission Internationale de l’Eclairage (CIE), that was introduced in 1931 and brought our colour awareness into the mathematical and calculable form (table of colour norm also known as „shoe sole“). CIELAB transforms the colour table norm into a (colour-) wheel. The contents of the shoe sole are so skewed by the formulas that the CIELAB-colour space better represents our perceptions. Thus equivalent colour differences are mirrored in approximately equidistant CIELAB-colour values, regardless of the colour space in which we are moving. CIELAB and Computer In the meantime the CIELAB-colour model has found its way into operating systems and software applications. Thus CIELAB-colour values can be directly input into programs such as Photoshop, CorelDRAW and others via Colourmanagement and the colours can also be accurately reproduced on printers, plotters, and monitors. Lab- und HLC-coordinates The colour values L, a and b are the right-angled coordinates in the CIELAB-colour space. HLC comes forth from the CIE-Lab-values through a simple calculation (Cartesian coordinates to polar coordinates). In contrast to the Lab-coordinates the HLC-values are clearly conceivable as primary colour, lightness and saturation of the relevant colour. Delta E The equally useable measure Delta E is the distance between two colours in the CIELAB-colourspace. The smaller Delta E is the better the two colours match. A Delta E under 1 contains an almost unseeable colour variance, a Delta E of 5 is clearly noticeable, but the two colours are still very similar.

The CIE Normfarbtafel. The CIELAB colour space.