The probe sends out white, high CRI LED light, arranged circularly to uniformly illuminate the skin. The emitted light is scattered in all directions, some parts travel through the layers and some is scattered out of the skin, the light reflected from the skin is measured in the probe and expressed accordingly.
Light points overlapping the closer the probe comes to the skin surface and different sizes of measurement tips help to place the Skin-Colorimeter Flex CL 440 perfectly on even smallest skin sites.
The raw data (XYZ-values) of the probe are corrected with a special colour matrix to be as close as possible to norm values. The measured colour can be calculated into different colour spaces.
RGB colour space: can be understood by thinking of it as all possible colours that can be made from three coloured lights for red, green, and blue.
The CIELAB color space (also known as L*a*b*) is a color space defined by the International Commission on Illumination (CIE). Each letter represents an axis. Correlation between the color space and the human skin:
- L* gives information about the black-white-axis, the brightness/ lightness, the higher L*, the brighter the skin.
- The a*-value located on green-red axis is proportional to the erythema (microcirculation/redness of the skin). A higher a* value corresponds to higher erythema.
- The b*-value located on the blue-yellow axis in literature often describes the pigmentation.
In addition the Individual Typology Angle ITA°
is automatically calculated from L* (luminance) and b* (yellow chromatic). ITA°
is an established tool to objectify skin colour for predicting the biological consequences of UV exposure on the skin (the lighter the skin, the higher the consequences).
- ITA° > 55° “very-light”
- 55° > ITA° > 41° “light”
- 41° > ITA° > 28° “intermediate”
- 28° > ITA° > 10° “tan”
- 10° > ITA° > - 30° “brown”
- - 30° > ITA° “dark”