Learning objectives
Knowledge of the principles and basic techniques to make colorimetric and reflectoscopic measurements on objects classified as cultural for knowledge purposes, diagnostic procedures for the conservation and restoration. Determination of optimal lighting situations of objects of art for the conservation, enjoyment and study.
Course unit content
Color physics of the non self-luminous objects and physical measurements<br />
- Optical properties and object visual properties. The light and the separation surface between two media. Light internal in a medium. Fluorescence. Light scattering. <br />
- Transparent media. Internal transmittance. Total transmittance and total reflectance.<br />
- Turbid media. Kubelka-Munck model. Saunderson Equation. Many flux models.<br />
- Physical quantities and geometrical standards for the color specification of non selfluminous objects. Light modulation in reflection and transmission. Gonio-apparent color and physical measurements<br />
Physiology of color vision.<br />
- Human eye. The optical system and the image formation. Chromatic aberrations. Optical densities of the optical media of the eye. <br />
- retina structure. <br />
- Photoreceptors, pigment properties, Rushton’s univariance principle. Photopic and scoptopic visions.<br />
- Gamut of light colors. Spectral colors, magenta, white. <br />
- color matching, metamerism, complementary colors. Additive color mixing.<br />
- Chromatic vision trivariance. The Young-Helmholtz theory.<br />
- Luminance contrast, contrast sensibility, luminance adaptation. Weber-Fechner laws. Luminance variations in space and in time. <br />
- Color of non self-luminous objects (white, gray, black, brown, etc). Neutral colors. Lightness scales. Mach’s bands. Color tree.<br />
- Hering’s opponent color theory. <br />
- Color vision deficiencies: anomalous trichromats and dichromats.<br />
- Chromatic adaptation, simultaneous and successive chromatic contrast, equiluminant stimuli and chromatic contrast sensibility. Chromatic adaptation chromatic contrast. <br />
- post-receptorial retinic functions, neural ways and cerebral areas specialized for the chromatic perception. <br />
Photometry <br />
- Photometric Unit: from historical candle to the International System. CIE 1924 photopic spectral luminous efficiency function. Photopic photometric standard observer CIE 1924 and CIE 1988. Luminous energy in the International System. Scotopic photometric standard observer CIE 1951. Photopic photometric observer with visual field of 10 ° CIE 2005. <br />
Colorimetry <br />
- Historical stages and systems of colorimetry. Modes to present the color and its nomenclature. <br />
- Psychophysical color space and standard CIE. Prereceptorial physics. Univariance Principle and space of activations of the cones. Chromaticity and chromaticity diagrams. Metamerism. Photometry and tristimulus space. CIE 1931 standard observer for visual field of 2 °. Modified 2 ° visual field Observer. CIE 1964 standard observer. Limitations of tristimulus space. <br />
- Spectral data, lighting and colorimetric calculations. Light sources and CIE standard illuminants. CIE color specification of a light source. Surface CIE color specification and optimal colors. Fluorescent color specification. Tint index and white index. Colorimetric calculations. <br />
- Psychometric Scales and CIE 1976 standard systems: Chromatic adaptation. Color discrimination and metric color space. CIE 1976 Systems: CIELUV and CIELAB. Specification of color difference. Metamerism indices. <br />
- Color ordering system and color Atlas. Mixture of dye systems. Color screen plate printing systems. Color mixing systems. Munsell color system. Swedish Natural Color System (NCS). System of the Optical society of America (OSA-UCS). DIN 6264 color system. <br />
Basic radiometric, photometric and colorimetric instrumentation.<br />
Light cabinet. Visual comparison instruments. Spectral weighing measuring instruments. Photometric instruments. Colorimetric instruments. Measurement tools for spectral analysis. Glossmeter.<br />
Color and lighting. <br />
Color temperature. Choosing the correct color temperature. Color rendering index. Limits on color rendition. Other parameters for the color rendering. Indices based on color preference. Indices based on discrimination of color. Influence of chromaticity sources on visual perception. Correlation between the yield of color and color temperature. Chromaticity of light and visual perception. Chromaticity sources and circadian cycle. <br />
Classic applications of colorimetry <br />
Monitor, camera and video signal. Monitor and video signal. Camera. sRGB system. Colorant Formulation. Screen plate printing.
Bibliography
a cura di C. Oleari, Misurare il colore, 2a edizione, Hoepli editore milano, 2008
