FACIAL SOFT BIOMETRICS - Library of Ph.D. Theses | EURASIP

20 2. SOFT BIOMETRICS: CHARACTERISTICS, ADVANTAGES AND RELATED WORKTable 2.1: Table of soft biometric traitsSoft Biometric Face / NatureSubjectivePermanence Distinctivenesstrait Accessory of value perceptionSkin color Face Continuous Medium Low MediumHair color Face Continuous Medium Medium MediumEye color Face Continuous High Medium MediumBeard Face Binary Low/Medium Low MediumMoustache Face Binary Low/Medium Low MediumFacialmeasurementsFace Continuous High Medium Medium/HighFacial shapes Face Discrete High High HighFacial featuremeasurementsFace Continuous High High Medium/HighFacial featureshapesFace Discrete High High HighMake–up Face Discrete Low Low MediumEthnicity Face Discrete High Medium MediumMarks Face Discrete High Medium/High LowGender Face Binary High Low LowAge Face Continuous Low/Medium Medium MediumGlasses Accessory Binary Low/Medium Low LowHat Accessory Binary Low Medium LowScarf Accessory Binary Low Medium Lowperception to the nature of value, where an increased amount of subcategories leads to a moredifficult classification. In fact subjectivity lays even in the decision of the nature of value. In otherwords, colors for example can be argued to be continuous, due to the huge variance in nuancesblending into each other, or to be discrete due to the fact that colors can be described by discreteRGB values.We note that soft biometrics can be classified by additional aspects such as accuracy and importance,which are deducible from the named classification classes, depending on the cause forspecification (e.g. suitability for a specific application).2.2 Characteristics, advantages and limitationsSoft biometrics has carried in some extent the attributes of classical biometrics over, as thegeneral idea of identification management based on who you are is still being pursuit. The traitsprovide weak biometrical information about the individual and correspondingly have inherited thepredicates to be universal, measurable and acceptable; furthermore the trait’s classification algorithm(s)performance should be able to meet the application’s requirements. To a certain degreealso the aspects uniqueness, permanence and circumvention play a role for soft biometrics, but aretreated to a greater extent flexible.Initially, soft biometric traits have been employed to narrow down the search of a database, in orderto decrease the computational time for the classical biometric trait. An additional application