Literature Review: Color Perception, Pigmentation and Optics

Jan 24, 2014 | Contact Author | By: Rachel L. Grabenhofer, Cosmetics & Toiletries
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Title: Literature Review: Color Perception, Pigmentation and Optics
agingx color perceptionx reflectancex opticsx metamaterialsx contrastx polymorphismx pigmentx sun spongex chromaticityx chromophoresx
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Keywords: aging | color perception | reflectance | optics | metamaterials | contrast | polymorphism | pigment | sun sponge | chromaticity | chromophores

Abstract: This survey of recent literature relates to color, optics and pigmentary mechanisms. The papers are presented as food for thought in the early stages of the product development process. Proposed applications are purely hypothetical but may warrant deeper investigation.

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R Grabenhofer, Literature Review: Color Perception, Pigmentation and Optics, Cosm & Toil 129(1-2) 46 (2014)

Compensating for aging-related loss of green tone color perception

S. Wuerger; Public Library of Science (PLOS); May 8, 2013

According to this research, peripheral vision declines with age due to a yellowing of the eye lens, which selectively reduces short wavelength light. In addition, cone receptor mechanisms in the eyes become less sensitive; however, one’s subjective experience of color generally does not change. Therefore, this 185-subject study sought to assess the extent to which the human visual system can subjectively compensate for such changes.

Results indicated that within the eye, at the threshold where acute vision occurs, color perception remained unaffected by yellowing of the lens, although the ability to discriminate between small color differences was compromised with increased age. Significant changes in color perception were only found for unique shades of green under daylight viewing conditions. This is consistent with the idea that the yellow-blue mechanism is affected most, due to selective attenuation of short-wavelength light.

These findings suggest a new approach toward the expression of certain green-colored cosmetics, or green products in general, aimed at an aging consumer demographic.

Reflectance vs. transmittance

H.J. Swatland; Color Research and Application, Early View (online first); Dec. 9, 2013

In the present publication, the author assessed the spectra of carmine, cochinilla rojo and rosada, and red annatto for reflectance and transmittance properties. In general, they strongly transmitted and reflected red light (> 640 nm), and strongly absorbed green light (520–560 nm). Carmine and cochinilla rosada had secondary peaks for transmittance and reflectance (~420 and 450 nm, respectively), whereas secondary peaks were not found for cochinilla rojo or red annatto. The scale of measurement, i.e., micro- vs. macro-scopic, and type, i.e., transmittance vs. reflectance, were of minor importance in colorimetry, a major effect was detected for light scattering. This points to the importance of measurement technique in color product development.

Zero-index optical metamaterials

H. Suchowski, K. O’Brien, Z.J. Wong, A. Salandrino, X. Yin and X. Zhang Science; Dec. 6, 2013

In Berkeley Lab’s Material Sciences Division, researchers used a unique material with a refractive index of zero to generate what they refer to as phase mismatch-free nonlinear light; i.e., light waves that, as they move through the material, gain strength in all directions. This capability could be employed in quantum computing and networking applications, or in future light sources based on nonlinear optics, such as those used to modify a material’s properties. For personal care, with the right modifications, applications such as triggered, sustained release could be an interesting proposition.

Facial contrast influences age perception

A. Porcheron, E. Mauger and R. Russell Public Library of Science (PLOS); March 6, 2013

Society generally behaves differently toward individuals based on their perceived age, and this perception relies on cues such as wrinkles. Here, researchers studied aspects of facial contrast, i.e., differentiation between facial features and the surrounding skin, in adult Caucasian women. Individual faces were perceived as being younger when the facial contrast was artificially increased, but older when the contrast was artificially decreased. Thus, facial contrast plays a role in age perception, suggesting the aim and role of cosmetics for making individuals appear younger.

Polymorphism in Interferon Regulatory Factor 4 (IRF4) to affect pigmentation

C. Praetorius et al.; Cell; Nov. 21, 2013

According to this work, IRF4 is a transcription factor with no known role in melanocyte biology, although it is associated with sensitivity of skin to sun exposure, freckles, blue eyes and brown hair color. Here, researchers found a single nucleotide polymorphism within a transcription enhancer of IRF4 in melanocytes. Assays in zebrafish and mice revealed that IRF4 cooperated with microphthalmia-associated transcription factor to activate the expression of tyrosinase. Such results demonstrate how a noncoding polymorphism can affect a human phenotype by modulating a developmental gene regulatory network.

These and other findings in molecular biology are gaining interest to develop cosmetics and personal care products. For example, during the December 2013 Society of Cosmetic Chemists (SCC) annual meeting, one pre-event class was dedicated to the subject. In relation, epigenetics and nutricosmetics have been a resurging topics of interest at both SCC and IFSCC conferences in recent years.

Designer chromophores to improve capture and delivery of solar energy

M.A. Harris et al.; Chem Sci; Aug. 6, 2013

In this published research, native bacterial light-harvesting peptides with covalently attached designer chromophores were developed to improve the capture of solar energy. These entities self-assemble with native peptides to form the structures found in plants and photosynthesizing bacteria, i.e., antennas. The biohybrid “sun sponges” have enhanced spectral coverage across the visible and near-infrared regions, compared with native antennas, and reportedly contribute to solar light harvesting via an energy-transfer cascade. The materials described suggest interesting applications, such as in UV protection.

Defining chromaticity coordinates

M.H. Brill; Color Research and Application, Early View (online first); Dec. 20, 2013

As is well-known in the personal care industry, the Comission Internationale de l’Eclairage (CIE) system defines chromaticity coordinates as the ratio of each of three value sets to their sum. As is shown in this article, for two-equation systems, there is always a tristimulus coordinate system that allows this definition to work. However, according to this author, to include systems in which three equations define chromaticity, an extension of the CIE definition would require a linear transformation that follows the ratio process. Such measurements greatly impact the design and results of color cosmetic efficacy.