Color Perception and Measurement

1. Color Perception and Measurement Foods / Biomaterials

9. Color • Important physical property • Determines acceptability of a food by a consumer – quality attribute in food, does not necessarily reflect nutritional, flavor, or functional values • Variety of systems used to describe color • Color order systems are 3-dimensional arrangements of color according to appearance – 5 color order systems for food

10. Tempting Vision thru Color • It’s not a secret that the way food looks has an effect on our willingness to eat it. That’s why top chefs spend so much time perfecting the presentation of their plates, and food companies spend so much money on marketing and packaging. Of course, taste is the most important sense when it comes to enjoying food, but just how important is sight? • Try this thought experiment: a bowl of yellow-colored gelatin is placed before you. How would you expect it to taste, sweet or sour? It could be that you think it will taste sour, because of your prior experience with other yellow foods that are sour, such as lemons and grapefruits. Or you could think it will taste sweet, based on your memory of other sweet foods that are yellow (like bananas or pineapple).

11. Color Basics • Color is the perceptual characteristic of light described by a color name. Specifically, color is light, and light is composed of many colors—those we see are the colors of the visual spectrum: red, orange, yellow, green, blue, and violet. Objects absorb certain wavelengths and reflect others back to the viewer. We perceive these wavelengths as color. • A color is described in three ways: by its name, how pure or desaturated it is, and its value or lightness. Although pink, crimson, and brick are all variations of the color red, each hue is distinct and differentiated by its chroma, saturation, intensity, and value.

12. Things required to see Color • A light source / illuminant • An object • An Observer • Color of a material becomes visible only when light from a luminous object or source illuminates or strikes the surface

14. Chroma, intensity, saturation and luminance/value are inter-related terms and have to do with the description of a color.

15. Chroma: How pure a hue is in relation to gray Saturation: The degree of purity of a hue. Intensity: The brightness or dullness of a hue. One may lower the intensity by adding white or black. Luminance / Value: A measure of the amount of light reflected from a hue. Those hues with a high content of white have a higher luminance or value.

16. Shade Tint Intensity Chroma

17. Shade and tint are terms that refer to a variation of a hue. • Shade: A hue produced by the addition of black. Tint: A hue produced by the addition of white.

18. Color measurement • Used if a correlation is present between colored component and chemical in food • Simpler and quicker than chemical analysis • Color changes occur in products during storage, maturation, processing, spoilage – potato chips • Color used to determine ripeness of fruits

20. Spectral Quality • Natural daylight varies greatly in spectral quality with direction of view, time of day and year, weather and geographical location • Simulated daylight is commonly used in industrial testing • Artificial light sources can be standardized and remain stable in quality

21. Measuring Color • Our perceptions and interpretations of color are highly subjective. Eye fatigue, age and other physiological factors can influence your color perception. • But even without such physical considerations, each observer interprets color based on personal references. • Each person also verbally defines an object's color differently. • As a result, objectively communicating a particular color to someone without some type of standard is difficult. • The color of many products acts as an important indicator of product quality and processing performance. There also must be a way to compare one color to the next with accuracy. • The solution is a measuring instrument that explicitly identifies a color. That is, an instrument that differentiates a color from all others and assigns it a numeric value.

22. How to Measure Color • Color Measuring Equipments • Spectrophotometers • Colorimeters

23. Spectrophotometer • Today, the most commonly used instruments for measuring color are spectrophotometers. • Spectro technology measures reflected or transmitted light at many points on the visual spectrum, which results in a curve. • Since the curve of each color is as unique as a signature or fingerprint, the curve is an excellent tool for identifying, specifying and matching color.

24. Colorimetry • Colorimetry, the science of color measurement, is widely employed in commerce, industry and the laboratory to express color in numerical terms and to measure color differences between specimens. • Applications include paints, inks, plastics, textiles and apparel, food and beverages, pharmaceuticals and cosmetics, displays, and other parts and products that reflect or transmit color.

25. Colorimetry • The use and importance of colorimetry has grown in unison with the increase of global manufacturing and processing. When plastic automotive trim produced on one continent, for example, must match a painted metal finish applied on another, an objective and precise description of color becomes an absolute necessity. • Unfortunately, human color perception varies widely and is affected by illumination, sample size, surrounding color and the angle of observation. Colorimetric instruments provide a set of standardized conditions that help assure consistency and repeatability.

26. Use of Color Specifically color is used in industry such as for: • Quality ControlTo check on contamination or degradation As an indication of suitability for a particular purpose As a guide to the condition of used product • RefiningAs a measure of progress in refining and processing Feedback for process control and optimisation Identification of product grade • Materials SourcingAn immediate guide to supply continuity • Inspection of Incoming materialsAssurance that materials meet color specifications • Production ControlA check for consistency within and across batches • Inspection of final productsConformance to predetermined color tolerances Compliance with customer specifications

28. ASSIGNMENTColor Order Systems • Munsell • CIE • CIE L*a*b* (CIELAB) • Hunter Lab • Lovibond