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How we see colour - Measuring and supplying correct colour
David Crowther

How we see colour can best be described as communicating colour. In the accompanying image of the rose at the bottom of this article, how would you describe the colour of this rose? Would you see it as yellow, sort of lemon yellow or maybe a bright canary yellow?

Your perception and interpretation of colour are highly subjective. Eye fatigue, age and other physiological factors can influence your colour perception. But even without such physical considerations, each observer interprets colour based on personal references.

Each person also verbally defines an object’s colour differently. As a result, objectively communicating a particular colour to someone without some type of standard is difficult. There also must be a way to compare one colour to the next with accuracy.

The solution is a measuring instrument that explicitly identifies a colour. That is, an instrument that differentiates a colour from all others and
assigns it a numeric value.

types of spectros copy.gifMethods to Measuring Colour
Spectrophotometers are the most commonly used instruments for measuring colour today. Spectro technology measures reflected or transmitted light at many points on the visual spectrum, which results in a curve. Since the curve of each colour is as unique as a signature or fingerprint, it is an excellent tool for identifying, specifying and matching colour.

The following information is provided as an outline to which type of instrument is the best choice for specific applications.

Spherically based instruments have played a major roll in formulation systems for nearly 50 years. Most are capable of including the “specular component” (gloss) while measuring. By opening a small trap door in the sphere, the “specular component” is excluded from the measurement. In most cases, databases for colour formulation are more accurate when this component is a part of the measurement. Spheres are also the
instrument of choice when the sample is textured, rough, or irregular or approaches the brilliance of a first surface mirror. Textile manufacturers, makers of roofing tiles or acoustic ceiling materials would all likely select spheres as the right tool for the job.

0/45 (or 45/0)
No instrument “sees” colour more like the human eye than the 0/45. This simply is because a viewer does everything in his or her power to exclude the “specular component” (gloss) when judging colour. When we look at pictures in a glossy magazine, we arrange ourselves so that the gloss does not reflect back to the eye. A 0/45 instrument, more effectively than any other, will remove gloss from the measurement and measure the appearance of the sample exactly as the human eye would see it.

In the past 10 or so years, car manufacturers have experimented with special effect colours. They use special additives such as mica, pearlescent materials, ground up seashells, microscopically coated coloured pigments and interference pigments to produce different colours at different angles of view. Large and expensive goniometers were traditionally used to measure these colours until X-Rite introduced a battery-powered, handheld, multi-angle instrument. X-Rite portable multi-angle instruments are used by many car manufacturers and their colorant supply chain, worldwide.

Colorimeters are not spectrophotometers. Colorimeters are tristimulus (three-filtered) devices that make use of red, green, and blue filters that emulate the response of the human eye to light and colour. In some quality control applications, these tools represent the lowest cost answer. Colorimeters cannot compensate for metamerism (a shift in the appearance of a sample due to the light used to illuminate the surface).
As colorimeters use a single type of light (such as incandescent or pulsed xenon) and because they do not record the spectral reflectance of the media, they cannot predict this shift. Spectrophotometers can compensate for this shift, making spectrophotometers a superior choice for accurate, repeatable colour measurement.

yellow rose_1 250.gif 
Note: The information and images contained in this article are reproduced with the permission of XRite Inc.

Integrated Colour – Throughout the Supply Chain
Since colour is a key element of a consumer’s buying decisions, how do you handle colour consistency and quality in a global environment? How do you keep in step with consumer colour preferences while ensuring colour options are available and easy to reproduce?
The solution is to have accurate and reliable colour measurement technology.

Accurate Colour. On Time. Every Time.
Whether you’re working with printed material, coatings, plastics or textiles, there are challenges unique to your business. Customer needs—not off-the-shelf products— will drive the solutions that best fits your business.

Colour measurement and control technology, with vertically integrated manufacturing capabilities and an industry largest global presence, should be at the top of your list when shopping for specific solutions.

When you streamline your workflow system, it can greatly reduce the complexity of your supply chain. With a digital supply chain solution for colour control, you can shift colour management responsibilities to your organisation.

This means you control colour data workflow. The result: data flows faster, which provides the information needed to optimize choice of suppliers, and respond quickly to market pressures.

David Crowther is the manager of Chromaticity Australia.
Chromaticity Australia offer colour management training and consulting.

David writes a regular Workshop page for Digital Reproduction magazine.