Method for analyzing hair

Method for analyzing a sample hair mixture having a mixture of two hair colors and an overall reflectance spectrum representative of said two colors, comprising:

• a) selecting a first reflectance spectrum representative of a first color in the hair mixture from a first group of spectrums;
• and
• iteratively for different colors:
• b) selecting a second reflectance spectrum representative of a second color in the hair mixture from a second group of spectrums;
• and
• c) calculating an optimized reflectance spectrum based on said first spectrum, said second spectrum, and a respective concentration of each of said first spectrum and second spectrum, said concentrations calculated to optimized fitness of said optimized reflectance spectrum to the overall spectrum;
• until finding an optimized spectrum best fitting said overall reflectance spectrum.

Method for analyzing a sample hair mixture having a mixture of two hair colors and an overall reflectance spectrum representative of said two colors, comprising:

• selecting a reflectance spectrum representative of colored hair such that said spectrum best fits the overall spectrum among a plurality of colored hair spectrums;
• comparing curvature of the overall reflectance spectrum with curvature of said selected spectrum;
• and
• finding a concentration of white hair color in the hair mixture according to said curvature comparison.

A method of dying hair having a mixture of two hair colors and an overall reflectance spectrum representative of said two colors, comprising:

• a) selecting a first reflectance spectrum representative of a first color in the hair mixture from a first group of spectrums;
• and
• iteratively for different colors:
• b) selecting a second reflectance spectrum representative of a second color in the hair mixture from a second group of spectrums;
• and
• c) calculating an optimized reflectance spectrum based on said first spectrum, said second spectrum, and a respective concentration of each of said first spectrum and second spectrum, said concentrations calculated to optimized fitness of said optimized spectrum to the overall spectrum;
• until finding an optimized spectrum best fitting said overall spectrum, and
• prescribing a hair dyeing treatment according to said found optimized spectrum.

A method of selecting dye ingredients for dyeing hair having a mixture of two hair colors and an overall reflectance spectrum representative of said two colors, comprising:

• a) selecting a first reflectance spectrum representative of a first color in the hair mixture from a first group of spectrums;
• and
• iteratively for different colors:
• b) selecting a second reflectance spectrum representative of a second color in the hair mixture from a second group of spectrums;
• and
• c) calculating an optimized reflectance spectrum based on said first spectrum, said second spectrum, and a respective concentration of each of said first spectrum and second spectrum, said concentrations calculated to optimized fitness of said optimized spectrum to the overall spectrum;
• until finding an optimized reflectance spectrum best fitting said overall spectrum, and
• prescribing ingredients for a hair dyeing treatment according to said found optimized reflectance spectrum.