There is more than one definition of the saturation of colour. In 2007 the author proposed a new formula for the saturation and in this presentation the experimental verification is shown.

Question: 

In the field of physiology there are not correct use of the terms saturation and chroma. Many of the physiologists only use the term saturation. If we add black to a colour the saturation changes only a little, but if we add white to a colour the saturation decreases. After adding more black to a colour the saturation also decreases and we arrive at a point where we have a coloured black. In 2007 the author proposed the following formula to describe saturation.

S = C / ([radic](C²+L²)) · 100 % (1)

In this formula C and L are chroma and lightness of a colour measured in the CIELAB-System. The formula proposed by the author is in agreement with the verbal definition of Manfred Richter: Saturation is the proportion of pure chromatic colour in the total colour sensation. The question is to show the experimental evidence of the formula.

Methodology: 

For the experimental verification we need visual scaling data of saturation assessed by subjects. Because good scaling data could not be found in the literature a new investigation has been accomplished. For this the Japanese colour system PCCS has been used. For visual scaling lines were drawn on a middle grey background. So we get a scale from 0 to 100 % from the left to the right. On the top left we put the white chart as 0 %. This is the zero point of the scale. Under the white chart we place some grey and at least the black chart. The persons now had to put the charts of the first hue on the grey paper and write down the values in a table. In the same way the next hues were scaled. The 14 persons making scaling had normal visual senses.

Results: 

The formula for the Saturation S is in agreement with the visual values of saturation.

Conclusion: 

The experiment shows that the proposed formula (1) can be used for calculating saturation from the measured values C_ab and L*. To have a formula to calculate saturation is useful for physiologists, designers and by controlling inking for instance printing.

Acknowledgment: 

I want to thank Prof. Schierz from the TU Ilmenau for supervising my habilitation and also the HTWK Leipzig and the Sächsischen Insitut für die Druckindustrie for supporting this work.