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Colorimetry

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	Colorimetry can refer to: the quantitative study of color Color Color or colour is the visual perception property corresponding in humans to the categories called red, yellow, blue and others.... perception. It is similar to spectrophotometry Spectrophotometry In physics, spectrophotometry is the quantifiable study of electromagnetic spectrum. It is more specific than the general term electromagnetic spectroscopy in that spectrophotometry deals with Visible spectrum light, near-ultraviolet, and near-infrared.... , but may be distinguished by its interest in reducing spectra to tristimulus values, from which the perception of color derives. the determination of the spectral absorbance Absorbance In spectroscopy, the absorbance A is defined as,where is the intensity of light at a specified wavelength ? that has passed through a sample and is the intensity of the light before it enters the sample or incident light intensity.... of a solution Solution In chemistry, a solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent.... . Instruments Colorimetric equipment is similar to that used in spectrophotometry. Some related equipment is also mentioned for completeness. A tristimulus colorimeter Colorimeter A colorimeter, an instrument used in colorimetry, can refer to one of several related devices.* In scientific fields the word generally refers to the device that measures the absorbance of particular wavelengths of light by a specific solution.... measures the tristimulus values of a color. A spectroradiometer Spectroradiometer Spectroradiometers are designed to measure the spectral power distributions of illuminants. They operate almost like spectrophotometers in the visible spectrum.... measures the absolute spectral radiance Radiance Radiance and spectral radiance are radiometry measures that describe the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle in a specified direction.... (intensity) or irradiance Irradiance Irradiance, radiant emittance, and radiant exitance are radiometry terms for the power of electromagnetic radiation at a surface, per unit area.... of a light source. A spectrophotometer measures the spectral reflectance, transmittance Transmittance In optics and spectroscopy, transmittance is the fraction of incident light at a specified wavelength that passes through a sample. Specifically, visible transmittance is this fraction for visible light.... , or relative irradiance of a color sample. A spectrocolorimeter is a spectrophotometer that can calculate tristimulus values. A densitometer Densitometer A densitometer is a Measuring instrument that measures the degree of darkness of a photographic or semitransparent material or of a reflecting surface.... measures the degree of light passing through or reflected by a subject. A color temperature meter measures the color temperature Color temperature Color temperature is a characteristic of visible light that has important applications in lighting, photography, videography, publishing, and other fields.... of an incident illuminant. Absorption colorimeter In physical chemistry Physical chemistry Physical chemistry is the application of physics to macroscopic, microscopic, atomic, subatomic, and particulate phenomena in chemical systems within the field of chemistry traditionally using the principles, practices and concepts of thermodynamics, quantum chemistry, statistical mechanics and kinetics.... , a colorimeter Colorimeter A colorimeter, an instrument used in colorimetry, can refer to one of several related devices.* In scientific fields the word generally refers to the device that measures the absorbance of particular wavelengths of light by a specific solution.... is a device used to test the concentration of a solution by measuring its absorbance of a specific wavelength of light. To use this device, different solutions must be made, and a control (usually a mixture of distilled water and another solution) is first filled into a cuvette Cuvette A cuvette is a kind of laboratory glassware, usually a small tube of circular or square cross section, sealed at one end, made of plastic, glass, or optical grade quartz glass and designed to hold samples for Spectroscopy experiments.... and placed inside a colorimeter to calibrate the machine. Only after the device has been calibrated can you use it to find the densities and/or concentrations of the other solutions. You do this by repeating the calibration, except with cuvettes filled with the other solutions. The filter on a colorimeter must be set to red if the liquid is blue. The size of the filter initially chosen for the colorimeter is extremely important, as the wavelength of light that is transmitted by the colorimeter has to be same as that absorbed by the substance. Tristimulus colorimeter In digital imaging Digital imaging Digital imaging or digital image acquisition is the creation of digital images, typically from a physical object. The term is often assumed to imply or include the digital image processing, , , digital printing, and display of such images.... , colorimeters are tristimulus devices used for color calibration Color calibration The aim of color calibration is to measure or adjust the color response of a device to establish a known relationship to a standard color space.... . Accurate color profiles ICC profile In color management, an ICC profile is a set of data that characterizes a color input or output device, or a color space, according to standards promulgated by the International Color Consortium .... ensure consistency throughout the imaging workflow, from acquisition to output. Spectroradiometer, Spectrophotometer, Spectrocolorimeter The absolute spectral power distribution Spectral power distribution In color science and radiometry, a spectral power distribution describes the power per unit area per unit wavelength of an illumination , or more generally, the per-wavelength contribution to any radiometric quantity .... of a light source can be measured with a spectroradiometer, which works by optically collecting the light, then passing it through a monochromator Monochromator A monochromator is an optics device that transmits a mechanically selectable narrow band of wavelengths of light or other radiation chosen from a wider range of wavelengths available at the input.... before reading it in narrow bands of wavelength. Reflected color can be measured using a spectrophotometer (also called spectroreflectometer or reflectometer), which takes measurements in the visible region (and a little beyond) of a given color sample. If the custom of taking readings at 10 nanometer increments is followed, the visible light range of 400-700nm will yield 31 readings. These readings are typically used to draw the sample's spectral reflectance Reflectivity In photometry and heat transfer, reflectivity is the fraction of incident radiation Reflection by a surface. In general it must be treated as a directional property that is a function of the reflected direction, the incident direction, and the incident wavelength.... curve (how much it reflects, as a function of wavelength); the most accurate data that can be provided regarding its characteristics. The readings by themselves are typically not as useful as their tristimulus values, which can be converted into chromaticity Chromaticity Chromaticity is an objective specification of the quality of a color regardless of its luminance, that is, as determined by its colorfulness and hue.... co-ordinates and manipulated through color space transformations. For this purpose, a spectrocolorimeter may be used. A spectrocolorimeter is simply a spectrophotometer that can estimate tristimulus values by numerical integration Numerical integration In numerical analysis, numerical integration constitutes a broad family of algorithms for calculating the numerical value of a definite integral, and by extension, the term is also sometimes used to describe the numerical ordinary differential equations.... (of the color matching functions' inner product with the illuminant's spectral power distribution). One benefit of spectrocolorimeters over tristimulus colorimeters is that they do not have optical filters, which are subject to manufacturing variance, and have a fixed spectral transmittance curve—until they age. On the other hand, tristimulus colorimeters are purpose-built, cheaper, and easier to use. The CIE recommends using measurement intervals under 5nm, even for smooth spectra. Sparser measurements fail to accurately characterize spiky emission spectra, such as that of the red phosphor of a CRT display, depicted aside. Color temperature meter Photographer Photographer A photographer is a person who takes a photograph using a camera. A professional photographer uses photography to make a living whilst an amateur photographer does not earn a living and typically takes photographs for pleasure and to record an event, place or person for future enjoyment.... s and cinematographer Cinematographer A cinematographer is one photography with a motion picture camera . The title is generally equivalent to director of photography , used to designate a chief over the camera and lighting film crews working on a film, responsible for achieving artistic and technical decisions related to the image.... s use information provided by these meters to decide what color correction Color correction Color correction by using color gels, or filters, is a process used in stage lighting, photography, television, cinematography and other disciplines, the intention of which is to alter the overall color of the light; typically the light color is measured on a scale known as color temperature, as well as along a green?magenta axis orthogonal t... should be done to make different light sources appear to have the same color temperature. If the user enters the reference color temperature, the meter can calculate the mired Mired Contracted from the term micro reciprocal degree, the mired is a unit of measurement used to express color temperature. It is given by the formula:... difference between the measurement and the reference, enabling the user to choose a corrective color gel Color gel A color gel or color filter , or a lighting gel or simply gel, is a transparency colored material that is used in theatre, event production, photography, videography and cinematography to color light and for color correction.... or photographic filter Photographic filter In photography, a filter is a camera accessory consisting of an filter that can be inserted in the optical path. The filter can be a square or rectangle shape mounted in a holder accessory, or, more commonly, a glass or plastic disk with a metal or plastic ring frame, which can be screwed in front of the Lens .... with the closest mired factor. Internally the meter is typically a silicon photodiode tristimulus colorimeter. The correlated color temperature can be calculated from the tristimulus values by first calculating the chromaticity Chromaticity Chromaticity is an objective specification of the quality of a color regardless of its luminance, that is, as determined by its colorfulness and hue.... co-ordinates in the CIE 1960 color space CIE 1960 color space The CIE 1960 color space is another name for the chromaticity space devised by David MacAdam.The CIE 1960 UCS does not define a luminance or lightness component, but the Y tristimulus value of the XYZ color space or a lightness index similar to W* of the CIE 1964 color space are sometimes used.... , then finding the closest point on the Planckian locus Planckian locus In color theory, the Planckian locus is generally the path or locus that the color of a black body would take ina particular color space as the blackbody temperature changes.... . See also Photometry Photometry (optics) Photometry is the science of measurement of light, in terms of its perceived brightness to the human eye. It is distinct from radiometry, which is the science of measurement of radiant energy in terms of absolute power; rather, in photometry, the radiant power at each wavelength is weighted by a luminosity function that models human b... Radiometry Radiometry In optics, radiometry is the field that studies the measurement of electromagnetic radiation, including visible light. Note that light is also measured using the techniques of photometry_, which deal with brightness as perceived by the human eye, rather than absolute power.... Further reading External links An informative brochure with background information and specifications of their equipment.