Ultraviolet plumage colors predict mate preferences in starlings

Avian plumage has long been used to test theories of sexual selection, with humans assessing the colors. However, many birds see in the ultraviolet (<400 nm), to which humans are blind. Consequently, it is important to know whether natural variation in UV reflectance from plumage functions in sexual signaling. We show that female starlings rank males differently when UV wavelengths are present or absent. Principal component analysis of ≈1300 reflectance spectra (300–700 nm) taken from sexually dimorphic plumage regions of males predicted preference under the UV+ treatment. Under UV− conditions, females ranked males in a different and nonrandom order, but plumage reflectance in the human visible spectrum did not predict choice. Natural variation in UV reflectance is thus important in avian mate assessment, and the prevailing light environment can have profound effects on observed mating preferences.

Analysis of the colorimetric properties of goniochromatic colors using the MacAdam limits under different light sources

Technological innovation in all areas has led to the appearance in recent years of new metallic and pearlescent materials, yet no exhaustive studies have been conducted to assess their colorimetric capabilities. The chromatic variability of these special-effect pigments may largely be due to the three-dimensional effect of their curved shapes and orientations when they are directionally or diffusely illuminated. Our study examines goniochromatic colors using the optimal colors (MacAdam limits) associated with normal colors (photometric scale of relative spectral reflectance from 0 to 1) under certain conventional illuminants and other light sources. From a database of 91 metallic and interference samples and using a multi-gonio-spectrophotometer, we analyzed samples with lightness values of more than 100 and others with lightness values of less than 100, but with higher chromaticities than optimal colors, which places them beyond the MacAdam limits. Our study thus demonstrates the existence of chromatic perceptions beyond the normal solid color associated with these materials and independent of the light source. The challenge for future research, therefore, is to replicate and render these color appearances in current and future color reproduction technologies for computer graphics.

Number of discernible colors for color-deficient observers estimated from the MacAdam limits

We estimated the number of colors perceived by color normal and color-deficient observers when looking at the theoretic limits of object-color stimuli. These limits, the optimal color stimuli, were computed for a color normal observer and CIE standard illuminant D65, and the resultant colors were expressed in the CIELAB and DIN99d color spaces. The corresponding color volumes for abnormal color vision were computed using models simulating for normal trichromatic observers the appearance for dichromats and anomalous trichomats. The number of colors perceived in each case was then computed from the color volumes enclosed by the optimal colors also known as MacAdam limits. It was estimated that dichromats perceive less than 1% of the colors perceived by normal trichromats and that anomalous trichromats perceive 50%–60% for anomalies in the medium-wavelength-sensitive and 60%–70% for anomalies in the long-wavelength-sensitive cones. Complementary estimates obtained similarly for the spectral locus of monochromatic stimuli suggest less impairment for color-deficient observers, a fact that is explained by the two-dimensional nature of the locus.

Manuel Martínez Torres. Retrat d'un que s'enamorà del dibuix i dels colors

Parte del catálogo de la exposición celebrada en Elche del 12 de Abril al 10 de Mayo de 2002.

Small sketch of woman. With notes on colors.

[From Jasper Cropsey Sketch book, 1855-1856]

Picturesque United States of America, 1811, 1812, 1813, being a memoir on Paul Svinin, Russian diplomatic officer, artist, and author, containing copious excerpts from his account of his travels in America, with fifty-two reproductions of water colors in his own sketch-book,

"A list of the editions of Svinin's pamphlet on General Moreau": p.45-46.

Water-colors : four Chinese tone poems /

For medium voice and piano.

Puck's domestic comedies; pictures in colors & black-&-white,

Mode of access: Internet.

The bantams down-to-date. A detailed description of the colors, types, standard points and weights of all the exhibition bantams; how to mate for the production of all breeds and varieties of game and "variety" bantams; inbreeding, double mating, the founding of strains and the creation of new species; housing, feeding, hatching; fitting for exhibition and general management; simplified doctoring of sick bantams.

Mode of access: Internet.

Recherches expérimentales sur la cause des changemens de couleurs dans les corps opaques et naturellement colorés /

Mode of access: Internet.

Supplement to "The art of graining" by Frederick Parsons : examples of grounds for various imitations specially matched to the author's colors, made in oil paint and contributed by Harrison Brothers & Co.

Mode of access: Internet.

The hardwood finisher, with rules and directions for finishing in natural colors and in antique, mahogany, cherry, birch, walnut, oak, ash, redwood, sycamore, pine and all other domestic woods. Also miscellaneous rules for filling, staining, varnishing, polishing, dyeing, gilding and bronzing; together with hints on the preparation of woodwork for the finisher.

Mode of access: Internet.

Nature neighbors, embracing birds, plants, animals, minerals, in natural colors by color photography;

"John James Audubon edition."

Manuel complet du verrier et du fabricant de glaces, cristaux, pierres précieuses factices, verres colorés, yeus artificiels, etc. /

Mode of access: Internet.