Textile coloration theory
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This document discusses color theory and spectrophotometry. It provides definitions for key color science terms like color, hue, fluorescence, and luminescence. It describes the basic components and functions of spectrophotometers, which are used to objectively measure color. Spectrophotometers analyze the spectral composition and wavelength of light to determine color properties. The document also outlines several color spaces like CIE 1931, L*a*b*, and L*C*h that are used to numerically define and compare colors in an objective, standardized way.
Textile coloration theory
- 2. Color is an aspect of visual perception dependent on the spectral composition of observed radiant energy. Color is physical impression of human mind. It is impossible to measure.
- 3. BASIC NORMS OF COLOR SCIENCE Color: The visual effect that is caused by the spectral composition of the light emitted, transmitted, or reflected by objects. Color Temperature A color temperature meter measures the color temperature of an incident illuminant.The temperature, in Kelvin, of a Planckian black body radiator whose radiation has the same chromaticity coordinates as that of a given stimulus. Fluorescence The process whereby colors absorb radiant power at one wavelength and immediately re-emit it at another (usually longer) wavelength, as in "day-glo" or black-light paints. Hue The attribute of a visual sensation according to which an area appears to be similar to one, or to proportion of two, of the unique hues: red, yellow, green and blue.
- 4. Light A universal and essential attribute of all perceptions and sensations that are peculiar to the visual system. In other words, an optical radiation capable of directly causing a visual sensation. Luminescence Luminescence may occur either during or after the absorption of light energy at another wavelength. Emission which occurs only as long as the exciting input is being received is specified by the term fluorescence; emission which continues for some time after the energy input has ceased (as on the dial of an alarm clock) is said to exhibit 'afterglow' or the attribute of so-called phosphorescence.
- 5. The wavelengths of the complete visible spectrum, between infrared and ultraviolet, range from approximately 390 to 750 nm (nanometers, billionths of a meter). Spectral wavelengths are also frequently given in Å (angstroms, 10 nm) or °K (degrees Kelvin). While active upon the human body, ultraviolet and infrared are invisible to the human eye. These are the wavelengths for the traditional visible "seven colors of the rainbow", VIBGYOR: 430-390 Violet 450-440 Indigo 480-460 Blue 530-490 Green 580-550 Yellow 640-590 Orange 750-650 Red
- 6. Color, wavelength, frequency and energy of light Color (nm) (THz) (μm−1) (eV) (kJ mol−1) Infrared >1000 <300 <1.00 <1.24 <120 Red 700 428 1.43 1.77 171 Orange 620 484 1.61 2.00 193 Yellow 580 517 1.72 2.14 206 Green 530 566 1.89 2.34 226 Blue 470 638 2.13 2.64 254 Violet 420 714 2.38 2.95 285 Near ultraviolet 300 1000 3.33 4.15 400 Far ultraviolet <200 >1500 >5.00 >6.20 >598
- 8. Spectrophotometer: The spectrophotometer is a physical tool which is eminently suited to measure the most important variable of all, the shade and strength of the dyestuffs themselves, whether they be in solution or on the fiber. Spectrophotometer used by dyeing factory and colorant manufacturers all over the world. Normally Color lab manager analysis the color of swatch with the help of spectrophotometer.
- 9. TYPES OF SPECTROPHOTOMETER Spectrophotometers measure reflected or transmitted light across a light spectrum. The resulting data creates a visual curve. Spectral data is invaluable to anyone in the printing trades. Spectral measurements ensure that color is consistent across varying substrates and production processes. A densitometer checks density but does not see color, and this can often result in color variations that might not meet customer expectations. Spherical Spectrophotometers
- 10. 0º/45º (OR 45º/0º) SPECTROPHOTOMETERS This is simply because a human viewer does everything in his or her power to exclude the “specular component” (gloss) when judging color. When we look at pictures in a glossy magazine, we arrange position so that the gloss does not reflect back to the eye. A 0º/45ºinstrument, more effectively than any other, will remove gloss from the measurement dynamics and measure the appearance of the sample exactly as the human eye would see it. Because 45° instruments perceive color in the same way as the human eye, they are generally preferred for applications such as measuring color on smooth or matte surfaces. They are not necessarily the best choice for measuring color on glossy and reflective surfaces.
- 11. MULTI-ANGLE SPECTROPHOTOMETERS Automotive manufacturers have created and refined automotive coatings to present a unique experience when viewing a vehicle. They have experimented with special effect colors using special additives such as mica, pearlescent materials, ground-up seashells, specially coated pigments in order to produce a surface that shifts in color when viewed from different angles. Large and expensive goniometers were traditionally used to measure these colors until X- Rite introduced a battery-powered, hand-held, multi-angle instrument.
- 12. Color measurement procedure consists of 5 steps: 1.Prepare samples to make colored compound 2.Make series of standard solutions of known concentrations and treat them in the same manner as the sample for making colored compounds 3.Set spectrophotometer to l of maximum light absorption 4.Measure light absorbance of standards 5.Plot standard curve: Absorbance vs. Concentration, Spectrophotometers measure reflected or transmitted light across a light spectrum. The resulting data creates a visual curve. Spectral measurements ensure that color is consistent across varying substrates and production processes. A densitometer checks density but does not see color, and this can often result in color variations that might not meet customer expectations.
- 13. Instruments for Measuring Transmittance The measurement of dyes in solution to verify the color quality and strength is themost common application, although the measurement of transparent films is also used. Most spectrophotometers for measuring liquids are designed such that a transmission cell or cuvet is inserted between the detector
- 15. Functions of spectrophotometer: 1.Color difference 2.Metamerism 3.Pass/fail operation 4.Fastness rating 5.Shade library 6.Cost comparison 7.Color match production 8.Reflectance curve.
- 16. Flow Chart of Color Matching Process with Spectrophotometer:
- 17. COLOR MEASUREMENTS The human eye has a spectral sensitivity that peaks at around 555 nm, which means that the color green gives an impression of higher brightness than other colors. At 490 nm the sensitivity is only 20% compared to the sensitivity at 555 nm. Furthermore, the human eye can only distinguish about 10 million different colors which is actually quite limited relative to the needs of color measurement applications. Spectrometers are designed to measure exact wavelengths, and are therefore ideal for color measurements. Color measurements may be applied to a variety of industrial applications such as color of textile, paper, fruit, wine, and bird feathers. Avantes has developed a variety of custom probes to meet the specific demands of the color measurement application. Color measurements are manifested in the L*a*b* color model which includes parameters for brightness and hue.
- 18. FIGURE : 1931 X,Y CHROMATICITY DIAGRAM Hue is the term used for general classification of color—the region of the visible spectrum (380 to 700 nm)—in which the greatest reflectance of light occurs. Hues perceived as blue tend to reflect light at the lower end of the spectrum, greens in the middle region, and reds toward the higher end. Above slide shows spectral sensitivity corresponding to that of the human eye.
- 19. X-Y-Z VALUES AND YXY COLOR SPACE One of the earlier color space representations is the CIE 1931X,Y chromaticity diagram, as shown in figure 2. The diagram is used for 2-D graphing of color, independent of lightness. X and Y are the chromaticity coordinates calculated from the tristimulus values X-Y-Z. In this diagram, achromatic colors are toward the center, and chromaticity increases toward the edges. A colorimetrically measured red apple whose chromaticity coordinates are X = 0.4832and Y = 0.3045can be located in this color space at position A (the blue circle). Also referred to as CIELAB, L*a*b* color space was promulgated in 1976 to adjust for one of the problems of the original Yxy color space. Equal distances on the X,Y chromaticity diagram did not correspond to equally perceived color differences. In the L*a*b* diagram, a spherical color solid, L* indicates lightness, and a* and b* are the chromaticity coordinates. Here the a* and b* indicate color directions (+a* is the red direction, -a* is the green direction).
- 20. L*C*h color space uses the same diagram as L*a*b* color space, but employs cylindrical rather than rectangular coordinates. L* is the same as the L* of the L*a*b* diagram. C* is chroma, and h is the hue angle. The value of C* is zero at the center for an achromatic color, and increases according to the distance from the center. Hue angle (h) is defined as starting at the +a* axis and is expressed in degrees as the chroma axis rotates counterclockwise. Measurement output from a colorimeter is expressed in terms of X-Y- Z values for the measured sample, as well as in units of other accepted uniform color spaces. By comparing measurements of target colors with sample specimens, the user obtains not only a numerical description of a color, but can also express the nature of a color difference between two measured specimens. The colorimeter pinpoints the difference in lightness, chromaticity, and hue between the target and the sample.
- 21. FIGURE 3: A*, B* CHROMATICITY DIAGRAM
- 22. Color measurements taken in one location and expressed in units of a given color space then can be compared with measurements taken in another location or at another time and communicated in an internationally accepted language. In this manner, colorimetric measurement eliminates subjectivity in color perceptions and color difference judgments. Color space A system for ordering colors that respects the relationships of similarity among them. There are variety of different color spaces, but they are all three dimensional. The two most widely known's of these methods are the Yxy color space, devised in 1931based on the tristimulus values XYZ defined by CIE, and the L*a*b* color space, devised in 1976to provide more uniform color differences in relation to visual differences. Color spaces such as these are now used throughout the world for color communication.
- 24. THE MUNSELL SCALE In 1905, artist Albert H. Munsell originated a color ordering system —or color scale — which is still used today. The Munsell System of Color Notation is significant from a historical perspective because it’s based on human perception. Moreover, it was devised before instrumentation was available for measuring and specifying color. The Munsell System assigns numerical values to the three properties of color: hue, value and chroma. Adjacent color samples represent equal intervals of visual perception. The model in Figure 4 depicts the Munsell Color Tree, which provides physical samples for judging visual color. Today’s color systems rely on instruments that utilize mathematics to help us judge color. Three things are necessary to see color: • A light source (illuminant) • An object (sample) • An observer/processor
- 25. THEORY OF COLOR MIXING
- 26. ADDITIVE O R LIGHT T H E O RY
- 27. SUBTRACTIVE O R PIGMENT T H E O RY
- 28. THREE DIMENSIONAL C O L O R SYSTEM
- 29. The most Popular Norm lights LightSource Specification ColorTemperature Day light D65 International standardArtificial daylight- 400-700nm 6500K Incandescent LightA CoolWhite Fluorescent.USA shoplight source-405,436,546 and 578nm 4200K Department store light-CWF /F2 Fluorescent Lamp 4230K Department store light-TL84/F11 Fluorescent Lamp 4o00K Ultraviolet Light-UV Ultraviolet lamp;365nm - Light source F Sun setting light .Yellow lightSource 2700K
- 31. PASS
- 33. WHEN CMC VALUE ISFAIL
- 34. Metamerism Index
- 35. THANK YOU