Principles of Light & Color
2Pages

Principles of Color Measurement Principles of Color Anatomy of the CIE Chromaticity Diagram Anatomy of the CIE Chromaticity Diagram Spectral Locus Spectral Locus Colors at maximum saturation. Colors at maximum saturation. Planckian Locus Planckian Locus Dominant Wavelength Dominant Color of light emitted by a black body at a given temperature. Color of light emitted by a black body at a given temperature. Used to calculate Correlated Color Temperature (CCT) of Used to calculate Correlated Color Temperature (CCT) of white light sources in Kelvin (K). white light sources in Kelvin (K). Intersection point on the spectral locus locus Intersection by a line originating at white and then then by a line projected through a given color. projected Purity (Excitation Purity) Purity The ratio of the distance of white to a a The ratio stimulus stimulus with respect to the distance of distance of white to white to the dominant wavelength on the on the spectral spectral locus (expressed as a percentage). percentage). Example Example Stimulus Stimulus MacAdam ellipses MacAdam ellipses dene areas of color on the CIE chromaticity diagram that are indistinguishable the human eye (ellipses shown here at ten times their actual size). indistinguishable toto the human eye (ellipses shown here atten times their actual size). 0.9 0.9y ưݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ˰ݑ ˰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ̰ݑ ̰ݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑͰݑ Cy=Y/((X+Y+Z)) Cy=Y/((X+Y+Z)) For a spectral power For a spectral power distribution (SPD), given distribution (SPD), given as , the XYZ tristimulus as ݑðݑðݑðݑðݑðݑ, the XYZ tristimulus values are computed as: values are computed as: Calculating CIE color coordinates of a stimulus: Calculating CIE color coordinates of a stimulus: Color gamut illustrates the RGB limits reproducible by digital displays. Color gamut illustrates the RGB limits reproducible by digital displays. 0.9 ٰݒڰݒڰݒڰݒڰݒڰݒڰݒ ڰݒ۰ݒ۰ݒ۰ݒ۰ݒ۰ݒ۰ݒ CIE Color CIE Color Matching Functions 2.0 2.0 Cx=X/((X+Y+Z)) Cx=X/((X+Y+Z)) Radiant Vision Systems engineers imaging colorimeters and photometers, application software, Radiant Vision Systems engineers imaging colorimeters and photometers, application software, and goniometric systems to critically evaluate light, color, and surface quality. Calibrated to and goniometric systems to critically evaluate light, color, and surface quality. Calibrated to simulate human visual perception, Radiant cameras perform scientic measurement of display

The Language of Light Luminous Flux (lumens) Luminous Intensity (candela) (candela per meter squared) (lumens per meter squared) Units of Measurement: Photometry Luminous Flux Luminous Intensity Spectral Power Distribution Every light source is defined by its unique spectral power distribution (SPD), which is the radiant power (Watts) emitted by the light source at each wavelength in the visible electromagnetic spectrum. Total output of a light source in all directions Luminous flux emitted per unit solid angle Photometry vs. Radiometry Total light output Light from a direction Light incident...