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Spectral Absorption (spectral + absorption)

Distribution by Scientific Domains

Medical Sciences	80%

Selected Abstracts

Developing beauty-enhancing makeup by controlling light reflected from skin (II) , a makeup foundation producing an optimal reflectance dip on skin

INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 4 2007
Y. Sakazaki
Spectral reflection curves of human skin generally show a characteristic dip in the 500,600 nm range. This ,dip' is unique for each person, and is believed to be caused by the spectral absorption of blood. We investigated the spectral reflectance of human skin and discovered a very interesting correlation between the area of the reflectance dip and L* value (lightness of the skin). The standard area of reflectance dip (Ads) is defined and calculated from the correlation we discovered. The actual area of reflectance dip (ADa) is calculated from the spectral reflection curve. The ratio of ADa and ADs was found to be a very useful optical parameter for skin complexion perception. By artificially creating different optical environments and varying ADa/ADs from 10 to 200%, we found that skin appeared more beautiful when ADa/ADs was in the 100,125% range. We therefore considered methods for applying these results into the development of cosmetic products. Investigation and testing of many different pigments resulted in the development of specially-designed powdered fiber with a #-shaped cross section dyed magenta. An experimental foundation with this powdered fiber produced a clear reflectance dip by raising reflectance in the short and long wavelength ranges. ADa/ADs increased from 49 to 107% without reducing lightness when this makeup foundation was applied on sallow skin. [source]

Sunscreens and UVA Protection: A Major Issue of Minor Importance,

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2001
Brian L. Diffey
ABSTRACT The ultraviolet A (320,400 nm) (UVA) exposure of sunscreen-protected skin depends not just on the absorption characteristics of the product but also on a number of other factors. These include the amount of sunscreen applied and how it is spread over the skin. The importance of the spectral absorption of a sunscreen compared with these other two variables in controlling cutaneous UVA exposure is examined here using an analysis of variance approach. The results demonstrate that by far the most important factor is the application of a liberal quantity of sunscreen. Less important is to spread it uniformly, and least important is the precise shape of the sunscreen-absorption spectrum, providing, of course, the spectrum extends into the UVA region. [source]

Pre-receptoral spectral absorption, healthy ageing and pre-clinical indications of retinal disease

ACTA OPHTHALMOLOGICA, Issue 2009
E KONSTANTAKOPOULOU
Purpose The aim of this study was to investigate how chromatic sensitivity changes as a function of age and to establish the extent to which such changes can be attributed to pre-receptoral spectral absorption of short wavelength light and/or changes in retinal mechanisms caused by ageing. Methods The absorption of blue light by the macular pigment (MP) and the crystalline lens and the subjects' sensitivity to rapid flicker were measured using the Macula Assessment Profile (MAP) test. Red-green (RG) and yellow blue (YB) chromatic detection thresholds were measured at the fovea for young and older subjects using the Colour Assessment and Diagnosis (CAD) test at 2.6, 26 and 65 cd/m2. The variables of interest included the spectral absorption of the lens, the optical density of the MP, subject's age and retinal illuminance. Results The absorption of blue light by the lens increased with age. Absorption of blue light by pre-receptoral filters did not affect RG chromatic sensitivity at any of the light levels investigated but had an effect on YB thresholds. The considerably higher colour vision thresholds of some subjects and the subsequent worsening of their chromatic sensitivity at the lower light level may reflect changes in the retina brought about by accelerated aging effects. Conclusion The effect of pre-receptoral absorption of blue light on chromatic sensitivity is small. Ageing affects the amount and spectral composition of the light reaching the photoreceptors and the processing of retinal signals. As a result, flicker sensitivity declines and colour vision deteriorates. Such effects arise mostly from changes in the retina. The MAP and CAD tests help us to detect the effects of accelerated ageing and retinal disease. [source]