Next RAL colours

This program helps you to find the matching RAL colour to a source colour.
This way you can determine exactly which RAL colour is closest to e.g. Oracal 052 and thus which RAL colour matches a film, facade or printing colour.

Which RAL colours are located near a comparison colour?

For users of colour measurement devices or in the case of pre-existing CIELAB-colour values (Lab or HLC) it is quick and unproblematic process to find the RAL-colours which have the most similarities to the original CIELAB-colour values. The RAL-colours which have the least CIELAB-colour distance to the originating colour is determined. The calculated colour distance to the originating colour is also indicated.

A visual inspection of the colour results using the original colour sample is essential.

Short instructions

1. Indicate the originating colour.
2. Select the RAL-colour system out of which the nearest colour should be searched for.
3. The nearest RAL-colours and their colour distance, Delta E, from the originating colour are calculated.

Colour distance Delta E

The colour gap Delta E is based on the definition from the International Lighting commission (Commission Internationale de l’Eclairage; CIE) from 1976 and is the common measure for colour variations in industrial practice. The smaller the Delta E, the better the match of the two colours. The calculation finds the colour tone with the smallest CIELAB colour gap Delta E to the starting colour. In the software an evaluation of the results takes place according to the following table:

 

This evaluation is only approximate in nature. The eye is much more sensitive to bright, unsaturated areas than it is to dark or heavily saturated colour areas. In other words: A Delta E = 2 leads to an obviously deviating colour when dealing with a pastel colour, whereas Delta E = 2 would be barely noticeable with a dark colour tones. The eye is also more sensitive when it comes to the orange and yellow colour areas than the Delta E value initially reveals.

In a few cases, especially those with large dE values, agreeing colours will be determined which, from the standpoint of visual perception, do not agree. In this way, the computer findes, e.g., for a HKS 18 K (L=25, a*=64, b*=5) the colour tone RAL 4004 Bordeaux Violet. In this case, the eye would sooner choose RAL 3004 Purple Red. This effect results primarily from the fact that the spacing formula (based on Hunter) gives the colour's brightness and colourfulness just as much weight in the evaluation as it does the colour type: HKS 18 K and RAL 4004 Bordeaux Violet actually agree quite well in saturation and brightness. Furthermore, a colour tone deviation in the inner region of the CIELAB colour space (with less colourful colours) only involves a very small dE difference although the actual colour difference is very visible.

Measurement Conditions

It is best to apply the measurement conditions used when determining the RAL-CIELAB colour values to the agreeing colours as well. This way, no uncontrollable results will be generated – otherwise it would be like comparing apples to oranges.

 

Measurement equipment: Datacolor SF 600X (RAL CLASSIC, RAL DESIGN System), Minolta CM 508d (RAL EFFECT)
Standard light D65
Measurement geometry = d / 8°
Standard observer according to CIE 1964
Measurement with gloss trap (without gloss inclusion)

 

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