With a worldwide market share in the tens of billions of US$ make-up is big business living on the promise of „improved appearance“. Besides this, skin care and other functions are a big revenue. Since beauty is in the eye of the beholder, the “improved appearance” is a sub-jective impression of the observer. It was the goal of this work to define an objective method of assessing this subjective impres-sion by technical means, to define the context of evaluation, and to apply a simple mathemati-cal model as proof of concept regarding feasibility of simulation.
Considerable effort was involved in the various areas of objectifying the visual impression of make-up on skin. This consisted of defining experimental setups for spectroscopic evaluation and standard photo-camera evaluation as well as cross-calibration of both setups with appro-priate reference standards ensuring traceability. It also involved the translation of radiometric properties (such as spectral flux) into their photometric counterparts (such as illuminance) in the context of colour theory and colorimetric “standard oberservers” as defined by CIE, the International Commission on Illumination. A separate effort was dedicated to characterize selected skin care products (make-up, cover-up, wrinkle eraser) in terms of their optical properties (absorption, scattering albedo). Both light and electron microscopy was employed to derive estimates on particle size and distribu-tion contained in these selected products to provide the basis for a mathematical model of light scattered by these products.
The final section of this work deals with modelling and simulation of “theoretical” make-up products based on modified model parameters. The emphasis here was on a “simple” model, not on a comprehensive simulation of all details of the visual impression created by skin cov-ered with make-up. This was intended as a proof of concept of the feasibility of employing comparatively simple scattering models to reproduce the key features of the visual impression both qualitatively (e.g. colour balance) and quantitatively (e.g. returned intensity of light). A well established model of light scattering by particles was chosen (primarily employed in at-mospheric scattering and adapted to make-up on skin) and input parameters for the model were derived from the physical properties obtained before.
Good agreement was achieved between experimental results and model within the limits of uncertainty. Various simulations of specific model parameters conclude the work. Though technical means and scientific methods – as have been employed in this work – might enhance the understanding of fundamental processes of light scattering responsible for the overall visual impression, the ultimate test will always be the subjective perception of the ob-server.
It has been satisfactorily noted at various points of this work that objective data does coincide with and support subjective visual impression. This work realizes a multi-disciplinary approach, touching upon various areas of expertise as outlined above. Diligence has been applied to provide full references for all technical and sci-entific literature quoted throughout the text.
Schmitzer, U., 2011. Die Physik des Make Up (Doctoral dissertation, uniwien).
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