Light interacts with hair fibers in a way that three different types of light are observed.
- A first reflection occurs when incident light is reflected on the surface of the fibers.
This reflection creates a shine band on hair. It has the same color as the incident light.
-A second reflection comes from the reflection of the transmitted light on the bottom surface of the fibers.
After reflection, the light is transmitted again outside the fibers.
This reflection (also called chroma or internal reflection) creates a band carrying color information specific to the fiber. It plays an important part in the visual appearance of hair.
-Diffused light can be observed when no direct light is sent to the fibers or as a background uniform color on
which reflections overlay. It comes from the internal scattering.
Diffused light is related to 'the hair color' (blond, red, black...).

SAMBA Hair system acquires successively 2 images of parallel and crossed polarization state. This allows the decomposition of the image seen by a conventional camera or the eye into 2 images: specular and diffused. The specular image is formed only by the light reflected by the hair surfaces (first and second reflection). This image contains the shine and chroma information. The diffused image is formed only by the scattered light coming from the inside of the hair. This image contains the color information. Assuming that the surface reflection does not contain color information, virtual images of SHINE and CHROMA are calculated from the specular image using a color based algorithm.  The shine image obtained is black & white, the Chroma image contains all color information. The light scattered by hair fiber can then be decomposed into 3 components: SHINE, CHROMA and DIFFUSED.
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