ABSTRACT
Introduction 882
Materials and Methods 883
UV Filters and Formulations 883
Measurement of UV Spectra 884
Measurement of UV-A Parameters 885
Introduction of Step Film Inhomogeneity by Mathematical Models 885
Calculation of Average UV Spectra from the Spectra of Individual
UV Filters 885
The Step Film Model by O’Neill 886
Using a Distribution Function for Introduction of Film Inhomogeneity 889
Correlation of Experimental and Calculated Data 891
Calculated SPF and SPF In Vivo 891
Correlation of Calculated UV-A Parameters and UV-A Parameters
Measured In Vitro 895
Summary 899
References 899
INTRODUCTION
The measure of the protection against sunburn achieved by application of
sunscreens is the sun protection factor (SPF). The SPF is defined as the ratio
of the minimal erythemal doses of solar radiation directed to human skin in the
presence and in the absence of a sunscreen (1).
