Friday, February 12, 2010

Color Matching in Textiles

Colour is one of the most fundamental aspects of textile design which contributes greatly to the overall visual effect of a finished fabric. Colour matching is a vital process in ensuring continuity of colour from the master standard to all subsequent production batches.
A variety of conditions affect how a color looks
1.Light- source difference
2.Observer Difference
3.Size Difference
4.Background Difference
5.Directional difference
How to Ensure Effective Color in Today's Manufacturing Processes?
The three components of colour matching
There are three components involved in colour viewing,which are  LIGHT, VISION and OBJECT. If any omponent changes, the actual perception of colour will also change.
It is important to keep the conditions (as mentioned above) constant when viewing colors.
Colour matching requires the use of a standard light box which has several illuminants:-

 Some of the standard light sources 

  • A - tungstun

  • CWF - Cool White Fluorescent

  • TL84,  

  • UV,

  • U30
Learn about Various Light Sources
Importance of color Management
Everybody's perception of colour is slightly different. Light boxes are therefore employed so that whenever samples are viewed the conditions are exactly the same.
Color Viewing booth / light box for color matching.

It's difficult to see the true color under different light sources in which measurement color deviation intends to occur when performing the color evaluation without a standard light sources. To simulate different light sources to obtain an objective color, color difference and color evaluation, we can put the test specimen into the color viewing booth / color light box, so that it's easily to see the true color daytime, night, indoor and outdoor, and ensure the color consistency.
The Problem of Metamerism
Metamerism in textile shade matching is defined as a phenomenon in which two colored objects appear same in one light source but differ when the light source is changed. This could be due to difference in pigments or materials.
The spectral reflectance characteristics of the colors of two objects are different , but the resulting tristimulus values are same in under one light source but different in another.
Color Measurement Methods for Textile Fabrics
Color Tolerances for Consistent Pass/Fail Decisions
Every colour has a colour space which can be pinpointed by coordinates given by a computer. Colour can also be checked by eye and given a colour space, but again this is open to subjectivity.
The three fundamental aspects of colour are lightness, chroma and hue.
Lightness( bright colors,dark colors,light colors, the lightness of color changes vertically) is shown on the "L" axis. It indicates the depth of a colour, ranging from white to black with grey in between. One way of picturing depth of colour would be to imagine a black and white photograph where every colour is shown as a different depth of black, white or grey. The lightness of the fabric sample would be represented by a number on the "L" axis.
Chroma or saturation ( Vivid colors, dull colors, chroma changes outward from the center) is shown as the distance away from the "L" axis.
If the colour is described as being at the very outside edge of chroma it will appear to the observer to be very clean and bright. As it moves towards the grey central "L" axis it will become greyer, flatter and more dirty.
Hue (Redder, greener, yellower, bluer etc. hues form the color wheel) is the variation in colour. For example, a blue may be very red - moving towards purple lilac - and would appear in the blue colour space at the red side. Different shades of blue would all appear in the blue colour space but in different areas.
Lightness, chroma and hue are checked on all yarns and piece dyed fabrics to ensure colour continuity standards are maintained to the highest levels. They can be represented as a three dimensional figure.

More Information on Color Theory

A Note on Color Inconstancy
Read Book on Color Space conversions
CIE color model

Complementary colors
Electromagnetic energy
HSV color model
Light primary colors
Print primary colors
Secondary colors

Background knowledge of different light sources
CIE Fluorescent Illuminants
Artificial Daylight D65 which corresponds to a mid-day sun in Western Europe / Northern Europe is a commonly-used standard illuminant defined by the CIE. It is part of the D series of illuminants that try to portray standard illumination conditions at open-air in different parts of the world. Artificial Daylight D65 light sources do not exist actually, only simulators. The quality of a simulator can be assessed with the CIE Metamerism Index. —CIE S005/E-1998.

TL84 - CIE Fluorescent Illuminants, Light Source (F11), TL84 light sources represent a tri-band fluorescent lamp. —CIE 1931.

CWF - CIE Fluorescent Illuminants, Light Source (F2), CIE F series light sources represent various types of fluorescent lighting. CWF(Cool White Fluorescent) light sources found in office environments.

Incandescent A - CIE Incandescent A is intended to represent typical, domestic, tungsten-filament lighting. Its relative spectral power distribution is that of a Planckian radiator at a temperature of approximately 2856 K. CIE standard Incandescent A should be used in all applications of colorimetry involving the use of incandescent lighting, unless there are specific reasons for using a different illuminant. It is found in our home.

UV - UV Ultra Violet Black light to reveal the presence of fluorescent dyes and bleaches.

U30/U35 - Neutral-white fluorescents have a CCT (Correlated color temperature) of 3000K or 3500K.

1 comment:

  1. Very nice article to learn about color. Wants to more related post, specially some important method to check and matching a color. Thanks.............


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